selftests: kvm: move vm_xsave_req_perm call to amx_test

mainline inclusion
from mainline-v5.17-rc1
commit dd4516ae
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I5RQLJ


CVE: NA

Intel-SIG: commit dd4516ae selftests: kvm: move vm_xsave_req_perm call to amx_test.

--------------------------------

There is no need for tests other than amx_test to enable dynamic xsave
states.  Remove the call to vm_xsave_req_perm from generic code,
and move it inside the test.  While at it, allow customizing the bit
that is requested, so that future tests can use it differently.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Lin Wang <lin.x.wang@intel.com>