proc: fix mount -t proc -o AAA

proc: fix mount -t proc -o AAA

The proc_parse_options() call from proc_mount() runs only once at boot
time.  So on any later mount attempt, any mount options are ignored
because ->s_root is already initialized.

As a consequence, "mount -o <options>" will ignore the options.  The
only way to change mount options is "mount -o remount,<options>".

To fix this, parse the mount options unconditionally.

Signed-off-by: Vasiliy Kulikov <[email protected]>
Reported-by: Arkadiusz Miskiewicz <[email protected]>
Tested-by: Arkadiusz Miskiewicz <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Valdis Kletnieks <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>