Introduce four lcd_syscalls for programming iommu for a pci device from LCD.
PCI devices can now be assigned to an LCD. During probe, one can assign a
device to a particular LCD. During device assignment, all pages inside the heap
and rammap regions are mapped in the iommu. During data plane operation, one
can map/unmap a page by means of lcd_syscall's.

Signed-off-by: Vikram Narayanan <vikram186@gmail.com>