[ARM] pxa/sharpsl_pm: merge the two sharpsl_pm.c since it's now pxa specific

collie_pm was the only non-PXA user of sharpsl_pm. Now as it's gone we
can merge code into one single file to allow further cleanup.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Eric Miao <eric.miao@marvell.com>