ALSA: emu10k1: validate parameters of snd_emu10k1_ptr_{read,write}()

Rather than applying masks to the provided values, make assertions
about them being valid - otherwise we'd just try to paper over bugs.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230514170323.3408798-2-oswald.buddenhagen@gmx.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>