input: synaptics_fw_update: Remove hardcoded firmware image name

Firmware name should be passed in based on target, not hardcoded.
Remove hardcoding and add appropriate error checking for this.

This is a propagated patch from msm-3.4 kernel
cb83583f41c3cfa50106645d920a3b7afffe17ba (input: synaptics_fw
_update: Remove hardcoded firmware image name).

Change-Id: Ia95bf2abf8a86adc649d64d757f22d84c8e0053f
Signed-off-by: Amy Maloche <amaloche@codeaurora.org>
Signed-off-by: Abinaya P <abinayap@codeaurora.org>