TI: Drop 'CONFIG_OMAP'

In the two cases in the code where we use CONFIG_OMAP as a useful test
currently we can make use of CONFIG_ARCH_OMAP2PLUS instead.  With that
changed we can drop all defines of CONFIG_OMAP.  While in here,
CONFIG_OMAP3430 is only defined and then never used, so drop.

Signed-off-by: Tom Rini <trini@konsulko.com>