KVM: selftests: arm64: Correct feature test for S1PIE in get-reg-list

The ID register for S1PIE is ID_AA64MMFR3_EL1.S1PIE which is bits 11:8 but
get-reg-list uses a shift of 4, checking SCTLRX instead. Use a shift of 8
instead.

Fixes: 5f0419a0083b ("KVM: selftests: get-reg-list: add Permission Indirection registers")
Signed-off-by: Mark Brown <broonie@kernel.org>