mtd: Fix device name leak when register device failed in add_mtd_device()

In the Linux kernel, the following vulnerability has been resolved:

mtd: Fix device name leak when register device failed in add_mtd_device()

There is a kmemleak when register device failed:

unreferenced object 0xffff888101aab550 (size 8):

comm "insmod", pid 3922, jiffies 4295277753 (age 925.408s)

hex dump (first 8 bytes):

6d 74 64 30 00 88 ff ff mtd0....

backtrace:

[<00000000bde26724>] __kmalloc_node_track_caller+0x4e/0x150

[<000000003c32b416>] kvasprintf+0xb0/0x130

[<000000001f7a8f15>] kobject_set_name_vargs+0x2f/0xb0

[<000000006e781163>] dev_set_name+0xab/0xe0

[<00000000e30d0c78>] add_mtd_device+0x4bb/0x700

[<00000000f3d34de7>] mtd_device_parse_register+0x2ac/0x3f0

[<00000000c0d88488>] 0xffffffffa0238457

[<00000000b40d0922>] 0xffffffffa02a008f

[<0000000023d17b9d>] do_one_initcall+0x87/0x2a0

[<00000000770f6ca6>] do_init_module+0xdf/0x320

[<000000007b6768fe>] load_module+0x2f98/0x3330

[<00000000346bed5a>] __do_sys_finit_module+0x113/0x1b0

[<00000000674c2290>] do_syscall_64+0x35/0x80

[<000000004c6a8d97>] entry_SYSCALL_64_after_hwframe+0x46/0xb0

If register device failed, should call put_device() to give up the

reference.