target-sparc: Use fprintf_function (format checking)

This change was missing in commit
9a78eead0c74333a394c0f7bbfc4423ac746fcd5.

Cc: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
