arm64: Expose ARMv8.5 CondM capability to userspace

ARMv8.5 adds new instructions XAFLAG and AXFLAG to translate the
representation of the results of floating point comparisons between the
native ARM format and an alternative format used by some software. Add
a hwcap allowing userspace to determine if they are present, since we
referred to earlier CondM extensions as FLAGM call these extensions
FLAGM2.

Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Documentation/arm64/elf_hwcaps.txt

@@ -207,6 +207,10 @@ HWCAP_FLAGM
 
     Functionality implied by ID_AA64ISAR0_EL1.TS == 0b0001.
 
+HWCAP2_FLAGM2
+
+    Functionality implied by ID_AA64ISAR0_EL1.TS == 0b0010.
+
 HWCAP_SSBS
 
     Functionality implied by ID_AA64PFR1_EL1.SSBS == 0b0010.