arm64/kvm: use {read,write}_sysreg()

A while back we added {read,write}_sysreg accessors to handle accesses
to system registers, without the usual boilerplate asm volatile,
temporary variable, etc.

This patch makes use of these in the arm64 KVM code to make the code
shorter and clearer.

At the same time, a comment style violation next to a system register
access is fixed up in reset_pmcr, and comments describing whether
operations are reads or writes are removed as this is now painfully
obvious.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/virt.h

@@ -46,6 +46,7 @@
 
 #include <asm/ptrace.h>
 #include <asm/sections.h>
+#include <asm/sysreg.h>
 
 /*
  * __boot_cpu_mode records what mode CPUs were booted in.
@@ -76,10 +77,7 @@ static inline bool is_hyp_mode_mismatched(void)
 
 static inline bool is_kernel_in_hyp_mode(void)
 {
-	u64 el;
-
-	asm("mrs %0, CurrentEL" : "=r" (el));
-	return el == CurrentEL_EL2;
+	return read_sysreg(CurrentEL) == CurrentEL_EL2;
 }
 
 #ifdef CONFIG_ARM64_VHE