-mregparm=3 has been enabled by default for some time on i386, and AFAIK
there aren't any problems with it left.

This patch removes the REGPARM config option and sets -mregparm=3
unconditionally.
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NAndi Kleen <ak@suse.de>