Input: atmel_mxt_ts - use client name for irq

The atmel_mxt_ts driver can support multiple devices simultaneously.
Use the i2c_client name instead of the driver name when requesting an
interrupt to make the different interrupts distinguishable in
/proc/interrupts and top.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>