omap: Split vmalloc.h for mach-omap1 and mach-omap2

Earlier patch "omap: Remap L3, L4 to get more kernel io address space"
changed the VMALLOC_END.

However, this change causes problems on mach-omap1:

BUG: mapping for 0xe0000000 at 0xe0000000 overlaps vmalloc space
BUG: mapping for 0xe1000000 at 0xe1000000 overlaps vmalloc space

Fix this by creating separate vmalloc.h files for mach-omap1
and mach-omap2.

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