input: atmel_mxt_ts: Re-parse IRQ to ensure correct mapping

Call irq_of_parse_and_map before requesting IRQ.  Without
this call, incorrect IRQ flags may be used.

Change-Id: I79672797c4b0209cfaec6b7912465725e8cb5d3d
Signed-off-by: Amy Maloche <amaloche@codeaurora.org>