ARM: OMAP1: CGRM: fix omap1_get_reset_sources() return type

An older version of the patch "ARM: OMAP1: create read_reset_sources()
function (for initial use by watchdog)" was sent upstream, which used
the wrong return type for the omap1_get_reset_sources() function.
Fix it to return a u32, which is what the WDTIMER platform_data
function pointer read_reset_sources() expects.

Signed-off-by: Paul Walmsley <paul@pwsan.com>