[MTD] [NOR] cfi_cmdset_0002.c: fix 'cfi_amdstd_erase_varsize' to be static

Make cfi_amdstd_erase_varsize static, as declared at the top
of the file to ensure sparse does not print a warning for an
undeclared function, as so:

drivers/mtd/chips/cfi_cmdset_0002.c:1612:5: warning: symbol 'cfi_amdstd_erase_varsize' was not declared. Should it be static?
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

drivers/mtd/chips/cfi_cmdset_0002.c

@@ -1609,7 +1609,7 @@ static int __xipram do_erase_oneblock(struct map_info *map, struct flchip *chip,
 }
 
 
-int cfi_amdstd_erase_varsize(struct mtd_info *mtd, struct erase_info *instr)
+static int cfi_amdstd_erase_varsize(struct mtd_info *mtd, struct erase_info *instr)
 {
 	unsigned long ofs, len;
 	int ret;