GICC_BPR has minimum legal values in secure and non-secure states.
'3' is the minimum BPR value leading to group and sub-group priority
as 'gggg.ssss'. In order to make an IRQ preemptible they need to
be in different priority group.
Hence to be generic priority values should be above '0x0f'.
IRQ0 - default priority (low prio)
IRQ1 - 0x0 (highest prio)
Signed-off-by: Sandeep Tripathy <sandeep.tripathy@broadcom.com>