[MIPS] Remove _fdata from asm-mips/sections.h

There is no _fdata symbol in kernel.
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

include/asm-mips/sections.h

@@ -3,6 +3,4 @@
 
 #include <asm-generic/sections.h>
 
-extern char _fdata;
-
 #endif /* _ASM_SECTIONS_H */