OMAP4: prm: Remove deprecated functions

The new prminst_xxx accessors based on partition and offset
is now used, so removed all the previous prcm_xxx accessors.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Rajendra Nayak <rnayak@ti.com>
[paul@pwsan.com: remove fn prototypes also]
Signed-off-by: Paul Walmsley <paul@pwsan.com>