mtd-rw: fix build failure with kernel 5.10

When building mtd-rw for a target based on Kernel 5.10 which has
CONFIG_MTD disabled the build fails with

ERROR: "put_mtd_device" [../mtd-rw.ko] undefined!
ERROR: "get_mtd_device" [../mtd-rw.ko] undefined!

Omit building the package for such a target.

Signed-off-by: David Bauer <mail@david-bauer.net>

kernel/mtd-rw/Makefile

@@ -10,7 +10,7 @@ include $(INCLUDE_DIR)/kernel.mk
 
 PKG_NAME:=mtd-rw
 PKG_VERSION:=git-20160214
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_MIRROR_HASH:=c44db17c3e05079116a1704f277642c9ce6f5ca4fa380c60f7e6d44509dc16be
@@ -29,6 +29,7 @@ define KernelPackage/mtd-rw
 	SUBMENU:=Other modules
 	TITLE:=Write-enabler for MTD partitions
 	FILES:=$(PKG_BUILD_DIR)/mtd-rw.ko
+	DEPENDS:=@!(TARGET_x86||TARGET_bcm27xx||TARGET_octeontx)
 endef
 
 define KernelPackage/mtd-rw/description

kernel/mtd-rw/patches/0001-mtd-disabled.patch

@@ -0,0 +1,24 @@
+--- a/mtd-rw.c
++++ b/mtd-rw.c
+@@ -54,7 +54,11 @@ MODULE_PARM_DESC(i_want_a_brick, "Make a
+ 
+ static int set_writeable(unsigned n, bool w)
+ {
++#ifndef CONFIG_MTD
++	struct mtd_info *mtd = -ENOSYS;
++#else
+ 	struct mtd_info *mtd = get_mtd_device(NULL, n);
++#endif
+ 	int err;
+ 
+ 	if (IS_ERR(mtd)) {
+@@ -76,7 +80,9 @@ static int set_writeable(unsigned n, boo
+ 		err = 0;
+ 	}
+ 
++#ifdef CONFIG_MTD
+ 	put_mtd_device(mtd);
++#endif
+ 	return err;
+ }
+