ARM: OMAP4: panda: add statics to remove warnings

Add statics to board-omap4-panda.c's internal functions and data
structures to remove sparse warnings:

arch/arm/mach-omap2/board-omap4panda.c:234:29: warning: symbol
'omap_panda_wlan_data' was not declared. Should it be static?
arch/arm/mach-omap2/board-omap4panda.c:441:24: warning: symbol
'omap4_panda_dvi_device' was not declared. Should it be static?
arch/arm/mach-omap2/board-omap4panda.c:451:12: warning: symbol
'omap4_panda_dvi_init' was not declared. Should it be static?
arch/arm/mach-omap2/board-omap4panda.c:512:13: warning: symbol
'omap4_panda_display_init' was not declared. Should it be static?

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>