Removing dead MACH_OMAP_H4_OTG

MACH_OMAP_H4_OTG doesn't exist in Kconfig, therefore removing all
references for it from the source code.

Signed-off-by: Christoph Egger <siccegge@cs.fau.de>
Signed-off-by: Tony Lindgren <tony@atomide.com>