Rework the Ti GPIO driver to work on multiple SoCs. At the moment it could
work with OMAP4 and AM335x without needing to recompile.

Reviewed by:	loos
Fix issue with restarting an "insb/insw/insl" instruction because of a page
fault on the destination buffer.

Prior to this change a page fault would be detected in vm_copyout(). This
was done after the I/O port access was done. If the I/O port access had
side-effects (e.g. reading the uart FIFO) then restarting the instruction
would result in incorrect behavior.

Fix this by validating the guest linear address before doing the I/O port
emulation. If the validation results in a page fault exception being injected
into the guest then the instruction can now be restarted without any
side-effects.