x86/hyperv: use helpers to read control registers in hv_snp_boot_ap()

Use native_read_cr*() helpers to read control registers into vmsa->cr*
instead of open-coded assembly.

No functional change intended, unless there was a purpose to specifying
rax.
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Link: https://lore.kernel.org/r/20240805201247.427982-1-yosryahmed@google.comSigned-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20240805201247.427982-1-yosryahmed@google.com>

arch/x86/hyperv/ivm.c

@@ -321,9 +321,9 @@ int hv_snp_boot_ap(u32 cpu, unsigned long start_ip)
 
 	vmsa->efer = native_read_msr(MSR_EFER);
 
-	asm volatile("movq %%cr4, %%rax;" : "=a" (vmsa->cr4));
-	asm volatile("movq %%cr3, %%rax;" : "=a" (vmsa->cr3));
-	asm volatile("movq %%cr0, %%rax;" : "=a" (vmsa->cr0));
+	vmsa->cr4 = native_read_cr4();
+	vmsa->cr3 = __native_read_cr3();
+	vmsa->cr0 = native_read_cr0();
 
 	vmsa->xcr0 = 1;
 	vmsa->g_pat = HV_AP_INIT_GPAT_DEFAULT;