ARM: OMAP: Fix path for omap-sha1-md5 import of irqs.h

Hi there,

This is my first kernel-type patch, so please go easy on me if I've made
any mistakes.  I recently tried building the master kernel from master
(commit e75343a207ef24490176abe3503743d7a006e299) and it failed at
omap-sha1-md5.c with a file not found issue (asm/arch-omap/irqs.h).    I
looked for a similar file, and figured that it meant
asm/plat-omap/include/mach/irqs.h, so I produced the patch below.
Hopefully that's the correct solution, but I'd appreciate it if someone
else could look it over too.  Thanks very much,

Mike  5:)

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