input: misc: pat9125: code clean-up in pat9125 driver

Remove redundant code from the Pixart PAT9125 reference driver
- Remove unwanted struct declarations and definitions
- Remove unwanted header files
- Dynamically allocate platform data structure
- Change pr_err to dev_err
- Changes as per Linux coding guidelines
- Clean-up probe and remove routines
- Remove unwanted file operations
- Remove unused functions and variables

Change-Id: I71b1d2548dc07c21ab8f12327662f5bb6998cdcb
Signed-off-by: Vevek Venkatesan <vevekv@codeaurora.org>
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>