fs/squashfs: sqfs_read: remove buggy offset functionality

fs/squashfs: sqfs_read: remove buggy offset functionality

offset is the offset in the file read, not the offset in the destination
buffer.
If the offset is not null, this will lead to a memory corruption.
So, for now, we are returning an error if the offset is used.

Signed-off-by: Richard Genoud <richard.genoud@posteo.net>
[jh80.chung: cherry picked from mainline commit 21b1b3bad58b50e5464b1bf016e7c96bf18ddb8d]
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Change-Id: Ie50645e5fcb2f06a21c8f88e16da9b0d1db35cca