keucr: use more specific max_t(int, ..

as advised by checkpatch, changed generic max(..) to max_t(int, ..

Signed-off-by: Laura Lawniczak <laura.lawniczak@googlemail.com>
Signed-off-by: Johannes Schilling <of82ecuq@cip.cs.fau.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>