Add Virtex4 and Virtex5 BSPs

This commit covers at least PR2020, 2022, and 2023. This
patch adds all of the code for both BSPs, modifications
to libcpu/powerpc for the ppc440, and some updates to the
BSPs from follow up review and testing.

These BSPs should be good baselines for future development.
The configurations used by Ric are custom and have a non-standard
NIC. They also do not have a UART.  Thus the current console
driver just prints to a RAM buffer.

The NIC and UART support are left for future work. When the UART
support is added, moving the existing "to RAM" console driver to
a shared location is likely desirable because boards with no debug
UART port are commonly deployed. This would let printk() go to RAM.

c/src/lib/libcpu/powerpc/shared/include/cpuIdent.h

@@ -35,12 +35,13 @@ typedef enum
   PPC_604e = 0x9,
   PPC_604r = 0xA,
   PPC_7400 = 0xC,
-  PPC_405  = 0x2001,
+  PPC_405  = 0x2001,  /* Xilinx Virtex-II Pro or -4 */
   PPC_405EX = 0x1291,	/* + 405EXr */
   PPC_405GP = 0x4011,	/* + 405CR */
   PPC_405GPr = 0x5091,
   PPC_405EZ = 0x4151,
   PPC_405EP = 0x5121,
+  PPC_440 = 0x7ff2,  /* Xilinx Virtex-5*/
   PPC_7455 = 0x8001, /* Kate Feng */
   PPC_7457 = 0x8002,
   PPC_620 = 0x16,