arm64: Expose DC CVAP to userspace

The ARMv8.2-DCPoP feature introduces persistent memory support to the
architecture, by defining a point of persistence in the memory
hierarchy, and a corresponding cache maintenance operation, DC CVAP.
Expose the support via HWCAP and MRS emulation.

Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/cpuinfo.c

@@ -68,6 +68,7 @@ static const char *const hwcap_str[] = {
 	"jscvt",
 	"fcma",
 	"lrcpc",
+	"dcpop",
 	NULL
 };