OMAP4: PRCM: Add offset defines for all PRM registers

The prm44xx.h files only had absolute register address
defines for all PRM registers.
This patch adds additional register offset defines for all the
registers, so they can be used with apis like prm_read_mod_*

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>