quota: Cleanup flags definitions

Currently all quota flags were defined just in kernel-private headers.
Export flags readable / writeable from userspace to userspace via
include/uapi/linux/quota.h.

Signed-off-by: Jan Kara <jack@suse.cz>

diff --cc fs/quota/dquot.c
Simple merge

diff --cc include/linux/dqblk_v1.h
Simple merge

diff --cc include/linux/quota.h
Simple merge

diff --cc include/uapi/linux/quota.h
Simple merge