CPU hotplug & cpuidle have some race condition when doing CPU hotplug
stress test. different CPU cores have the chance to access the same
GPC register(A53_AD), so lock is necessary to do exlusive access.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Change-Id: I1296592e05fa78429c3f0fac066951521db755e3

The number of gpc imr mask reg & the offset is different
on some SOC, so correct it & replace the magic number with
macro define.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Change-Id: Ic701675cdd92e043dcd7f06722f2e871068aec74

Keep A53 PLAT(SCU) power domain on in wait mode(ret).
RBC count only need to be set in PLAT OFF mode, so
change it accordingly.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Change-Id: Ie55e25c8210d298506fc4dca7a9653583db45e0c

for the i.MX8M SOCs, part of the code for gpc
and PSCI implementation can be reused and make it
common for all these SoCs. this patch extracts
the common part for reuse.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>