MFC r256670:
Rewrite RDRAND support:
Remove the excessive memory accesses to temporary buffer.
Streamline the assembly and unify it between i386 and amd64.

Approved by:	re (glebius)
MFC r257069:
Add ddb 'show ioapic' and 'show all ioapics' commands.

Approved by:	re (glebius)
MFC r257070:
Move the PCI_DMA_BOUNDARY definition into the pcivar.h.

Approved by:	re (glebius)
MFC r257071:
Add some definitions for the bits in root control and status PCIe cap
registers.

Approved by:	re (glebius)
MFC r257072:
Make pci_get_dma_tag() non-static.

Approved by:	re (glebius)