generic/765: modify some steps to fix test

generic/765: modify some steps to fix test

Now that multi-block atomics writes are supported, some of the test steps
are failing. Those steps relied on supporting single-block atomic writes
only.

The current test steps are as follows:
a. Ensure statx for bdev returns same awu_min/max as from sysfs
b. test mkfs for each size of bdev atomic writes capabilities and supported
   FS block size
c. Ensure atomic limits for file match block size for each in b.
d. Ensure that we can atomic write block size for each in b.
e. Ensure that we cannot write file for 2* bdev awu_max or bdev awu_max /2

Make test pass again by:
1. Modify c. to ensure file awu_max >= block size
2. dropping e. We already have tests to ensure that we can only write a
   size >= awu_min and <= awu_max in generic/767

Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>