omap4: Drop redundant CONFIG_OMAP4430 symbol

While there are a few different OMAP4 SoCs, today we always set
CONFIG_OMAP4430 and CONFIG_OMAP44XX.  Convert the few test of
CONFIG_OMAP4430 to CONFIG_OMAP44XX.

Cc: Marek Vasut <marex@denx.de>
Cc: Paul Kocialkowski <contact@paulk.fr>
Signed-off-by: Tom Rini <trini@konsulko.com>