cgpt: find: filter out more devices before touching them

A partition's name would always start with the disk name. And in
/proc/partitions, the partitions are always listed right after the
disk.

Let's filter out devices which are not followed by partitions when
go through the /proc/partitions.

BUG=chrome-os-partner:62955
TEST=run "cgpt find -t kernel" on kevin, no more this warning:
blk_update_request: I/O error, dev mmcblk0rpmb

Change-Id: If200a2476d26b1beaf644838d47ea2e60552855e
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Reviewed-on: https://chromium-review.googlesource.com/444492
Reviewed-by: Julius Werner <jwerner@chromium.org>
1 file changed