Input: cypress_ps2 - use u8 when dealing with byte data

When dealing with byte data use u8 instead of unsigned char or int.
Stop layering error handling in cypress_ps2_sendbyte() and simply
pass on error code from ps2_sendbyte().

Additionally use u8 instead of unisgned char throughout the code.

Link: https://lore.kernel.org/r/20240628224728.2180126-5-dmitry.torokhov@gmail.com


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>