chore(lib/s2tt): move HIPAS and RIPAS fields

- Move HIPAS field to bits [5:3], corresponding to
MemAttr[3:1] of 2 block and page descriptors.
- Move RIPAS field with defined values in range
[0-3] to bits [2:1] corresponding to MemAttr[0]
and block/page descriptor select bit.
- RIPAS and DESC_TYPE fields share bit[1], bit[0]
set to 1 applies to a valid descriptor with HIPAS
and RIPAS fields N/A.

Signed-off-by: AlexeiFedorov <Alexei.Fedorov@arm.com>
Change-Id: Ib045a4586c15d854b53c787100b3043dd22f1213
2 files changed