ehf: use common priority level enumuration

'EHF' is used by RAS, SDEI, SPM_MM common frameworks.
If platform needs to plug-in specific handlers then
'PLAT_EHF_DESC' can be used to populate platform specific
priority levels.

Signed-off-by: Sandeep Tripathy <sandeep.tripathy@broadcom.com>
Change-Id: I37af7e0e48111f87b6982604bf5c15db3e05755d
4 files changed