Bluetooth: Fix crash in the Marvell driver initialization codepath

btmrvl_add_card() function calls kthread_run that might return error
(e.g. if current thread is killed). If one tries to use the error
value as a pointer then invalid memory access oops happens.

Check kthread_run() return value, if it is an error then release resources
correctly.

TEST=boot computer with BT modules enabled. I see the error message that
BT device initialization failed. Now kernel does not crash. Hint: to enable
BT run 'rmmod btmrvl_sdio; modprobe btmrvl_sdio'

Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>