Linux Header: Remove unused OSL prototypes.

This patch removes 2 useless OSL prototypes as they are not used by Linux now.
Lv Zheng.
Add validation of the XSDT root table if present.

Some platforms contain an XSDT that is ill-formed or otherwise invalid
(such as containing some or all entries that are NULL pointers).
This change adds a new function to validate the XSDT before actually
using it. If the XSDT is found to be invalid, ACPICA will now fall
back to using the RSDT instead. Original implementation by Zhao Yakui.
Ported to ACPICA and enhanced by Lv Zheng and Bob Moore.
Add option to ignore XSDT and force the use of the RSDT.

This change adds a runtime option that will force ACPICA to use the
RSDT instead of the XSDT. Although the ACPI spec requires that an XSDT
be used instead of the RSDT, the XSDT has been found to be corrupt or
ill-formed on some machines. Lv Zheng.