ARM: davinci: board-da830-evm: fix unused const variable warning

da830_evm_emif25_pins[] is used only when CONFIG_DA830_UI_NAND
is enabled. It gives the following warning when the config is
switched off. Fix it.

arch/arm/mach-davinci/board-da830-evm.c:245:20: warning: ‘da830_evm_emif25_pins’ defined but not used [-Wunused-const-variable=]
 static const short da830_evm_emif25_pins[] = {
                    ^~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Sekhar Nori <nsekhar@ti.com>