OMAP2xxx clock: move the APLL clock code into mach-omap2/clkt2xxx_apll.c

Move the APLL-related clock functions from clock2xxx.c to
mach-omap2/clkt2xxx_apll.c.  This is intended to make the clock code
easier to understand, since all of the functions needed to manage APLLs
are now located in their own file, rather than being mixed with other,
unrelated functions.

Clock debugging is also now more finely-grained, since the DEBUG
macro can now be defined for APLL clocks alone.  This
should reduce unnecessary console noise when debugging.

Also, if at some future point the mach-omap2/ directory is split
into OMAP2/3/4 variants, this clkt file can be placed in the mach-omap2xxx/
directory, rather than shared with other chip types that don't use this
clock type.

Thanks to Alexander Shishkin <virtuoso@slind.org> for his comments to
improve the patch description.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Richard Woodruff <r-woodruff2@ti.com>
Cc: Alexander Shishkin <virtuoso@slind.org>