remoteproc/omap: fix a sparse warning

This patch fixes a sparse warning in the omap remoteproc code
when OMAP_REMOTEPROC is disabled.

include/linux/platform_data/remoteproc-omap.h:76:13: warning: symbol 'omap_rproc_reserve_cma' was not declared. Should it be static?

Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>