cmd: ubi: Remove useless call to mtdparts_init()

Commit c58fb2cd ("cmd: ubi: clean the partition handling")
introduced a call to mtd_probe_devices() in the ubi_attach() path
and this function takes care of parsing mtdparts/mtdids and
creating/registering the associated mtd partitions.

The mtdparts_init() call in the ubi_detach() path is not only
unnecessary but can sometimes print error messages even when things
work properly (that's the case with SPI NAND devices that have not
been probed with 'mtd list'), which is misleading.

Remove this call to mtdparts_init() and drop the dependency on
CMD_MTDPARTS.

Fixes: c58fb2cd ("cmd: ubi: clean the partition handling")
Reported-by: Stefan Roese <sr@denx.de>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Tested-by: Stefan Roese <sr@denx.de>
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Jagan Teki <jagan@openedev.com>

cmd/Kconfig

@@ -1856,7 +1856,6 @@ endmenu
 
 config CMD_UBI
 	tristate "Enable UBI - Unsorted block images commands"
-	select CMD_MTDPARTS
 	select CRC32
 	select MTD_UBI
 	help

cmd/ubi.c

@@ -417,11 +417,6 @@ static int ubi_dev_scan(struct mtd_info *info, const char *vid_header_offset)
 
 int ubi_detach(void)
 {
-	if (mtdparts_init() != 0) {
-		printf("Error initializing mtdparts!\n");
-		return 1;
-	}
-
 #ifdef CONFIG_CMD_UBIFS
 	/*
 	 * Automatically unmount UBIFS partition when user