input: touchscreen: Clean code for i2c_read and i2c_write

Use standard initializer code in gtp_i2c_read and
gtp_i2c_write functions for Goodix touchscreen driver.

CRs-fixed: 549289
Change-Id: Id954be61a0b4596339a659928fb630c5c5538a9a
Signed-off-by: Shantanu Jain <shjain@codeaurora.org>