->permission() sanitizing: don't pass flags to exec_permission()

pass mask instead; kill security_inode_exec_permission() since we can use
security_inode_permission() instead.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc fs/namei.c
Simple merge

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

diff --cc security/security.c
Simple merge