The code for setting G0 and G1 is duplicated -- for each of them. Move
the code to a separate function (vc_setGx) and distinguish the two cases
by a parameter.

Change if-else-if to switch which allows for slightly better
optimization (decision tree).
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200615074910.19267-4-jslaby@suse.czSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>