uapi/linux/quota.h: Do not include linux/errno.h

linux/errno.h is very sensitive to coordination with libc headers.
Nothing in linux/quota.h needs it, so this change allows using
this header in more contexts.

Signed-off-by: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>