KVM: arm64: Fix some documentation build warnings

As warned with make htmldocs:

	.../Documentation/virt/kvm/devices/vcpu.rst:70: WARNING: Malformed table.
	Text in column margin in table line 2.

	=======  ======================================================
	-ENODEV: PMUv3 not supported or GIC not initialized
	-ENXIO:  PMUv3 not properly configured or in-kernel irqchip not
	         configured as required prior to calling this attribute
	-EBUSY:  PMUv3 already initialized
	-EINVAL: Invalid filter range
	=======  ======================================================

The ':' character for two lines are above the size of the column.
Besides that, other tables at the file doesn't use ':', so
just drop them.

While here, also fix this warning also introduced at the same patch:

	.../Documentation/virt/kvm/devices/vcpu.rst:88: WARNING: Block quote ends without a blank line; unexpected unindent.

By marking the C code as a literal block.

Fixes: 8be86a5e ("KVM: arm64: Document PMU filtering API")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/b5385dd0213f1f070667925bf7a807bf5270ba78.1601616399.git.mchehab+huawei@kernel.org

Documentation/virt/kvm/devices/vcpu.rst

@@ -67,25 +67,25 @@ irqchip.
 :Returns:
 
 	 =======  ======================================================
-	 -ENODEV: PMUv3 not supported or GIC not initialized
-	 -ENXIO:  PMUv3 not properly configured or in-kernel irqchip not
+	 -ENODEV  PMUv3 not supported or GIC not initialized
+	 -ENXIO   PMUv3 not properly configured or in-kernel irqchip not
 	 	  configured as required prior to calling this attribute
-	 -EBUSY:  PMUv3 already initialized
-	 -EINVAL: Invalid filter range
+	 -EBUSY   PMUv3 already initialized
+	 -EINVAL  Invalid filter range
 	 =======  ======================================================
 
-Request the installation of a PMU event filter described as follows:
+Request the installation of a PMU event filter described as follows::
 
-struct kvm_pmu_event_filter {
-	__u16	base_event;
-	__u16	nevents;
+    struct kvm_pmu_event_filter {
+	    __u16	base_event;
+	    __u16	nevents;
 
-#define KVM_PMU_EVENT_ALLOW	0
-#define KVM_PMU_EVENT_DENY	1
+    #define KVM_PMU_EVENT_ALLOW	0
+    #define KVM_PMU_EVENT_DENY	1
 
-	__u8	action;
-	__u8	pad[3];
-};
+	    __u8	action;
+	    __u8	pad[3];
+    };
 
 A filter range is defined as the range [@base_event, @base_event + @nevents),
 together with an @action (KVM_PMU_EVENT_ALLOW or KVM_PMU_EVENT_DENY). The