OMAP2xxx: clock: add clockfw autoidle support for APLLs

OMAP2xxx devices have two on-chip APLLs.  These APLLs can
automatically enter idle when not in use.  Connect the APLL autoidle
code to the clock code, so that the clock framework can handle this
process.  As part of this patch, remove the code in mach-omap2/pm24xx.c
that previously handled APLL autoidle control.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Kevin Hilman <khilman@ti.com>
Tested-by: Rajendra Nayak <rnayak@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>