ARM: davinci: Don't rely on public mmc header to include interrupt.h

The davinci board omapl138-hawk, depends on interrupt.h. Explicitly include
it instead of relying on the public mmc header host.h.

Cc: Sekhar Nori <nsekhar@ti.com>
Cc: Kevin Hilman <khilman@kernel.org>
Cc: <linux-arm-kernel@lists.infradead.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Sekhar Nori <nsekhar@ti.com>