ARM: omap2: include linux/errno.h in hwmod_reset

The newly created omap_hwmod_reset.c is missing an
include of linux/errno.h in commit c02060d8 "ARM:
OMAP4+: AESS: enable internal auto-gating during
initial setup". It still works in omap2_defconfig,
but not in all other combinations.

Without this patch, building allmodconfig results in:

arch/arm/mach-omap2/omap_hwmod_reset.c: In function 'omap_hwmod_aess_preprogram':
arch/arm/mach-omap2/omap_hwmod_reset.c:47:11: error: 'EINVAL' undeclared (first use in this function)
arch/arm/mach-omap2/omap_hwmod_reset.c:47:11: note: each undeclared identifier is reported only once for each function it appears in

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Tony Lindgren <tony@atomide.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Sebastien Guiriec <s-guiriec@ti.com>