ALSA: usx2y: Avoid camelCase

For improving readability, convert camelCase fields, variables and
functions to the plain names with underscore.  Also align the macros
to be capital letters.

All done via sed, no functional changes.

Note that you'll still see many coding style issues even after this
patch; the fixes will follow.

Link: https://lore.kernel.org/r/20210517131545.27252-2-tiwai@suse.de


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