Input: melfas_mip4 - mark a bunch of variables as __always_unused

Input: melfas_mip4 - mark a bunch of variables as __always_unused

Dmitry requested to keep these around for the purposes of documentation.

Fixes the following W=1 kernel build warning(s):

 drivers/input/touchscreen/melfas_mip4.c: In function ‘mip4_report_touch’:
 drivers/input/touchscreen/melfas_mip4.c:474:5: warning: variable ‘size’ set but not used [-Wunused-but-set-variable]
 drivers/input/touchscreen/melfas_mip4.c:472:5: warning: variable ‘pressure_stage’ set but not used [-Wunused-but-set-variable]
 drivers/input/touchscreen/melfas_mip4.c:469:7: warning: variable ‘palm’ set but not used [-Wunused-but-set-variable]
 drivers/input/touchscreen/melfas_mip4.c:468:7: warning: variable ‘hover’ set but not used [-Wunused-but-set-variable]

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210114152323.2382283-3-lee.jones@linaro.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>