sparc: Fix broken memset for sparc32 [BZ #31068]

Fixes commit a61933fe ("sparc: Remove bzero optimization") that
after moving code jumped to the wrong label 4.

Verfied by successfully running string/test-memset on sparc32.

Signed-off-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: Ludwig Rydberg <ludwig.rydberg@gaisler.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
(cherry picked from commit 578190b7)