mtd: Rename free() to rfree()

This function name conflicts with our desire to #define free() to
something else on sandbox. Since it deals with resources, rename it to
rfree().

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/mtd/nand/spi/micron.c b/drivers/mtd/nand/spi/micron.c
index 83951c5..9c24542 100644
--- a/drivers/mtd/nand/spi/micron.c
+++ b/drivers/mtd/nand/spi/micron.c
@@ -63,7 +63,7 @@
 
 static const struct mtd_ooblayout_ops mt29f2g01abagd_ooblayout = {
 	.ecc = mt29f2g01abagd_ooblayout_ecc,
-	.free = mt29f2g01abagd_ooblayout_free,
+	.rfree = mt29f2g01abagd_ooblayout_free,
 };
 
 static int mt29f2g01abagd_ecc_get_status(struct spinand_device *spinand,