btrfs: get the device in write mode when deleting it
btrfs: get the device in write mode when deleting it

When we're deleting the device we should get it in write mode since
we're going to re-write the super block magic on that device. And it
should fail if the device is read-only.

Signed-off-by: Lukas Czerner <6c9141d0e2318b390a8a6bf8ecd9f819d16f05b4@redhat.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas