pkeys: Reserve PKEY_DISABLE_READ

[Florian Weimer]

* Ram Pai:

> Ok. here is a patch, compiled but not tested. See if this meets the
> specifications.
>
> -----------------------------------------------------------------------------------
>
> commit 3dc06e73f3795921265d5d1d935e428deab01616
> Author: Ram Pai <linuxram at us.ibm.com>
> Date:   Tue Dec 4 00:04:11 2018 -0500
>
>     pkeys: add support of PKEY_DISABLE_READ

Thanks.  In the x86 code, the translation of PKEY_DISABLE_READ |
PKEY_DISABLE_WRITE to PKEY_DISABLE_ACCESS appears to be missing.  I
believe the existing code produces PKEY_DISABLE_WRITE, which is wrong.

Rest looks okay to me (again not tested).

Thanks,
Florian