ARM: OMAP2+: clean up omap_hwmod.o build directives in Makefile

Move the omap_hwmod_common_data.o build directive down to the hwmod
data Makefile section where it belongs.  Move the omap_hwmod.o build
directive to the top 'Common support' line, since we have no separate
hwmod code Makefile section, and it's currently needed for all OMAP2+.

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