perf test record user-regs: Fix mask for vg register

perf test record user-regs: Fix mask for vg register

The 'vg' register for arm64 shows up in --user_regs as available when
masking the variable AT_HWCAP with 1 << 22 returns '1' as done in
perf_regs.c.

However, in subtests for support of SVE, the check for the 'vg' register
is done by masking the variable AT_HWCAP with the value 0x200000 which
is equals to 1 << 21 instead of 1 << 22.

This results in inconsistencies on certain systems where the test
expects that the 'vg' register is not operational when it is, and
vice-versa.

During the testing on a machine that the test expected not to have the
'vg' register available, 'perf record' with the option --user-regs
showed records for the 'vg' register together with all of the others,
which means that the mask for the subtest of perf_event_attr is off by
one.

Change the value of the mask from 0x200000 to 0x400000 to correct it.

Fixes: 9440ebdc333dd12e ("perf test arm64: Add attr tests for new VG register")
Reviewed-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Veronika Molnarova <vmolnaro@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Link: https://lore.kernel.org/r/20231201194617.13012-1-vmolnaro@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>