[SME] Add tests for SME and SME2 functionality

The tests check if SME and SME2 is usable from userspace.
The following features are tested:
- HWCAP2 flags and ID_AA64PFR1_EL1 register
- Instructions for entering and leaving Streaming SVE mode
- SME vector length setting via prctl
- An SME operation (addha) and the result of it
- An SME2 operation (umopa) and the result of it
- Access to SME2 ZT0 storage

Change-Id: If179f3c1b2204e34e6cc5dd5e78fdb6e23c3f255