arm64: Allow 48-bits VA space without ARM_SMMU

Now when KVM has been reworked to support 48-bits host VA space, we can
allow systems to be configured with this option.  However, the ARM SMMU
driver also needs to be tweaked for 48-bit support so only allow the
config option to be set when not including support for theSMMU.
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/Kconfig

@@ -232,7 +232,7 @@ config ARM64_VA_BITS_42
 
 config ARM64_VA_BITS_48
 	bool "48-bit"
-	depends on BROKEN
+	depends on !ARM_SMMU
 
 endchoice