ARM: OMAP2+: make dra7xx_sha0_hwmod static

The dra7xx_sha0_hwmod object is not exported outside of
omap_hwmod_7xx_data. so make it static to avoid the
following warning:

arch/arm/mach-omap2/omap_hwmod_7xx_data.c:686:19: warning: symbol 'dra7xx_sha0_hwmod' was not declared. Should it be static?

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>