ARM: OMAP4+: Make secondary_startup function name more consistent

Current code has rather inconsistent function names for 'secondary_startup'
routines. Update it to make it more consistent.

Suggested by Kevin Hilman as part of OMAP5 PM patch review.

Cc: Kevin Hilman <khilman@deeprootsystems.com>

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Kevin Hilman <khilman@linaro.org>