arm64: spe: Add EL1 test for misprogramming the buffer pointer

There are two rules that software must follow when programming the buffer
pointer:

- The current write pointer must be at least one sample record below the
  write limit pointer
- Bits [63:56] of PMBPTR_EL1 and PMBLIMITR_EL1.LIMIT must match.

If any one of the rules is not followed, than the behaviour is
UNPREDICTABLE, and one of two things might happen:

- A buffer management event is generated, which can be one of buffer full
  event or an MMU fault.
- SPE can write to any writable address.

KVM injects a buffer full management event in these cases, add a test
for both rules.