target-xxx: Use fprintf_function (format checking)

fprintf_function uses format checking with GCC_FMT_ATTR.

Format errors were fixed in
* target-i386/helper.c
* target-mips/translate.c
* target-ppc/translate.c

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