ARM: OMAP2+: add missing lateinit hook for calling pm late init

AM335x, AM43xx, OMAP5 and DRA7 have missing late init hook. Introduce
SoC specific hook with a call to OMAP2+ generic lateinit hook. This
allows the generic late initializations such as cpufreq hooks to be
active.

Based on out-of-tree patches that need to be introduced in
mainline, this introduction allows us to provide the foundation for
further SoC specific features as they are developed.

Cc: Benoit Cousson <bcousson@baylibre.com>
Cc: Kevin Hilman <khilman@deeprootsystems.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>