input: touchscreen: synaptics_dsx: Stack memory allocation fixes

Move I2C read/write buffers from stack to heap memory synaptics_dsx
touch driver, to support GSI mode in buses required for Secure
Touch feature.

Change-Id: I18dbd122aae3818c85dd01cc5e9139edf5f94197
Signed-off-by: Ritesh Kumar <riteshk@codeaurora.org>