sparc: Use swap() to fix Coccinelle warning

Fixes the following Coccinelle/coccicheck warning reported by
swap.cocci:

	WARNING opportunity for swap()

Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Reviewed-by: Andreas Larsson <andreas@gaisler.com>
Link: https://lore.kernel.org/r/20240404112313.11898-2-thorsten.blum@toblux.com


Signed-off-by: Andreas Larsson <andreas@gaisler.com>