Stop layering error handling in cypress_ps2_sendbyte() and simply
pass on error code from ps2_sendbyte() and use it in the callers.

This fixes mishandling of error condition in
cypress_ps2_read_cmd_status() which expects errors to be negative.
Reported-by: Igor Artemiev <Igor.A.Artemiev@mcst.ru>
Link: https://lore.kernel.org/r/20240628224728.2180126-2-dmitry.torokhov@gmail.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>