input: touchscreen: request threaded-only IRQs with IRQF_ONESHOT

Threaded IRQs without primary handler need to be requested with
IRQF_ONESHOT, otherwise the request will fail. This patch adds the
IRQF_ONESHOT to the focaltech touchscreen driver where it is
missing.

Change-Id: I429f48126bd5d28c6dbf6ba846175d5e643dd436
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>