ANDROID: nvmet: Use the bdev_is_zone_start() function

Add support for zone sizes that are not a power of two in nvmet.

Bug: 269471019
Bug: 415836627
Change-Id: I7ec207985799d3c7a82d26033b87e37b51935640
Signed-off-by: Bart Van Assche <bvanassche@google.com>