block: Handle error case when bdi_register_owner() fails

Fix the below issue observed when bdi_register_owner() fails
in device_add_disk().

Unable to handle kernel paging request at virtual address
pc : sysfs_do_create_link_sd+0x50/0x100
lr : sysfs_do_create_link_sd+0x40/0x100
...
Call trace:
 sysfs_do_create_link_sd+0x50/0x100
 sysfs_do_create_link+0x78/0x90
 sysfs_create_link+0x38/0x48
 device_add_disk+0x5b8/0xad8
 loop_add+0x4a0/0x6cc
 loop_control_ioctl+0x164/0x2b8
 vfs_ioctl+0x7c/0xb4
 do_vfs_ioctl+0x868/0x1384
 SyS_ioctl+0x6c/0xa4

Change-Id: Ibd814b207047537dacdca73a75299cbac3c361b7
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>