feat(cpufeat): added few helper functions

Following utility functions/bit definitions done
 - Write a helper function to return the presence of following features
    - FEAT_UAO
    - FEAT_EBEP
    - FEAT_SEBEP
    - FEAT_SSBS
    - FEAT_NMI
    - FEAT_PAN
 - Add definition of some missing bits of SPSR.
 - Add GCSCR_EL1 register encoding and accessor function.

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: Ifcead0dd8e3b32096e4ab810dde5d582a889785a
6 files changed