nand.h: Cleanup linux/mtd/rawnand.h usage

We only include <linux/mtd/rawnand.h> in <nand.h> for the forward
declaration of struct nand_chip, so do that directly.  Then, include
<linux/mtd/rawnand.h> where required directly.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/mtd/nand/raw/stm32_fmc2_nand.c b/drivers/mtd/nand/raw/stm32_fmc2_nand.c
index e17f1f8..eee6594 100644
--- a/drivers/mtd/nand/raw/stm32_fmc2_nand.c
+++ b/drivers/mtd/nand/raw/stm32_fmc2_nand.c
@@ -19,6 +19,7 @@
 #include <linux/err.h>
 #include <linux/iopoll.h>
 #include <linux/ioport.h>
+#include <linux/mtd/rawnand.h>
 
 /* Bad block marker length */
 #define FMC2_BBM_LEN			2