ARM: OMAP2+: Remove legacy macros for zoom platforms

Commit 97411608 ("ARM: OMAP2+: Remove legacy support for zoom
platforms") removed the Kconfig symbols MACH_OMAP_ZOOM2 and
MACH_OMAP_ZOOM3. Remove the last usage of the related macros too.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Tony Lindgren <tony@atomide.com>