ARMV7: OMAP: Fix build after introduction of GENERATED_GBL_DATA_SIZE

This patch fixes the issue by defining and using CONFIG_SYS_INIT_RAM_SIZE and
CONFIG_SYS_INIT_RAM_ADDR. Based on an email discussion with Wolfgang Denk and
Heiko Schocher.

Signed-off-by: Steve Sakoman <steve.sakoman@linaro.org>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>