ARM: tegra: decouple mode from flags

When doing LP2 on last standing CPU, we currently pass
"mode | flag" to a few functions as argument, with the
assumption that "mode" will be confined to lower 22 bits
in PMC_CTRL register and "flags" will occupy higher 10
bits. If "flags" grows downward or "mode" grows upward,
without this explicit knowledge, LP2 will break on the
last standing CPU. Therefore we need to decouple them.

Currently only "flags" part is being used when passed to
other subroutines, so use "flags" only.

Change-Id: I299c998145d81c17760bda8a0b56311fed553958
Signed-off-by: Bo Yan <byan@nvidia.com>
Reviewed-on: http://git-master/r/100358
Reviewed-by: Simone Willett <swillett@nvidia.com>
Tested-by: Simone Willett <swillett@nvidia.com>

Conflicts:

	arch/arm/mach-tegra/pm.c