Revert "Revert "Fix derp from previous ion commits""

This reverts commit 6978fccb032d4d78f6c4415896618113c55e4dad.
Revert "ion: Add reserve function to ion"

This reverts commit 5576c66b9401413684c6d82c573004c294cc2024.
Revert "ion: Switch map/unmap dma api to sg_tables"

This reverts commit 9ad6684dc50e35af452e37da6f3ae92e2ece4ba2.

Conflicts:
	include/linux/ion.h