ARM: OMAP2+: Fix L4_EMU_34XX_BASE error after iomap changes

With the introduction of iomap changes platform init code
fails for emu.c if CONFIG_OMAP3_EMU is selected:

arch/arm/mach-omap2/emu.c:35:8: error:
'L4_EMU_34XX_BASE' undeclared here (not in a function)

Signed-off-by: Tony Lindgren <tony@atomide.com>