Input: synaptics-rmi4 - make array rmi_f54_report_type_names static

The array rmi_f54_report_type_names is local to the source and does
not need to be in global scope, so make it static. Also make the array
const char * const.

Cleans up sparse warning:
symbol 'rmi_f54_report_type_names' was not declared. Should it be static?

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>