OMAP4: prcm: Fix global warm reset bit position

OMAP4 platform has different register bits for Warm and Cold Resets.
Write one into appropriate bits.

Signed-off-by: Rajeev Kulkarni <rajeevk@ti.com>
Cc: Leed Aguilar <leed.aguilar@ti.com>
[b-cousson@ti.com: Change the define with the proper one from omap4 headers]
Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Tested-by: Kevin Hilman <khilman@deeprootsystems.com>