gpio: Fix stmpe error path

Free allocated memory.  Call stmpe_disable() if it was enabled.

Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>