ARM: export set_irq_flags

The recently added Emma Mobile GPIO driver calls set_irq_flags
and irq_set_chip_and_handler for the interrupts it exports and
it can be built as a module, which currently fails with

ERROR: "set_irq_flags" [drivers/gpio/gpio-em.ko] undefined!

We either need to replace the call to set_irq_flags with something
else or export that function. This patch does the latter.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Magnus Damm <damm@opensource.se>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>