cmd/misc: Stop using a function pointer

Currently, enabling CMD_MISC gives:
cmd/misc.c:67:25: warning: assignment to 'int (*)(struct udevice *, int,  void *, int)' from incompatible pointer type 'int (*)(struct udevice *, int,  const void *, int)' [-Wincompatible-pointer-types]

Because 'misc_read' takes a void * and 'misc_write' takes a const void
*, both of which make sense for their operation.  Given there's one
place we make use of the function pointer, just call read or write
directly for the operation we're called with.

Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Sean Anderson <seanga2@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/cmd/misc.c b/cmd/misc.c
index bcd8d96..ec32b41 100644
--- a/cmd/misc.c
+++ b/cmd/misc.c
@@ -44,7 +44,6 @@
 static int do_misc_op(struct cmd_tbl *cmdtp, int flag,
 		      int argc, char *const argv[], enum misc_op op)
 {
-	int (*misc_op)(struct udevice *, int, void *, int);
 	struct udevice *dev;
 	int offset;
 	void *buf;
@@ -62,11 +61,10 @@
 	size = hextoul(argv[3], NULL);
 
 	if (op == MISC_OP_READ)
-		misc_op = misc_read;
+		ret = misc_read(dev, offset, buf, size);
 	else
-		misc_op = misc_write;
+		ret = misc_write(dev, offset, buf, size);
 
-	ret = misc_op(dev, offset, buf, size);
 	if (ret < 0) {
 		if (ret == -ENOSYS) {
 			printf("The device does not support %s\n",