MIPS: Rename the "Fill" cache ops to avoid build failure

MIPS define a "Fill" macro as a cache operation in cacheops.h, this
will cause build failure under some special configurations because in
seq_file.c there is a "Fill" label. To avoid this failure we rename the
"Fill" macro to "Fill_I" which has the same coding style as other cache
operations in cacheops.h (we think renaming the "Fill" macro is more
reasonable than renaming the "Fill" label).

Callers of "Fill" macro is also updated.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>