arch: arm64: mpu: Fix mpu init assertion fail

During mpu init, we check MSA_frac bits[55:52] and MSA bits[51:48] of
the ID_AA64MMFR0_EL1 register. Currently we only allow 1F to pass the
check. But according to Armv8-R AArch64 manual [1], both 1F and 2F
indicates the processor supports MPU. This commit aims at fixing this.

[1]: https://developer.arm.com/documentation/ddi0600/latest/



Signed-off-by: Jaxson Han <jaxson.han@arm.com>