ppc4xx: Clean up 440 exceptions handling

- Introduced dedicated switches for building 440 and 405 images required
  for 440-specific machine instructions like 'rfmci' etc.

- Exception vectors moved to the proper location (_start moved away from
  the critical exception handler space, which it occupied)

- CriticalInput now serviced (with default handler)

- MachineCheck properly serviced (added a dedicated handler and return
  subroutine)

- Overall cleanup of exceptions declared with STD_EXCEPTION macro (unused,
  unhandled and those not relevant for 4xx were eliminated)

- Eliminated Linux leftovers, removed dead code

Signed-off-by: Grzegorz Bernacki <gjb@semihalf.com>
Signed-off-by: Rafal Jaworowski <raj@semihalf.com>
Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/include/configs/sequoia.h b/include/configs/sequoia.h
index 23243a4..42b42fc 100644
--- a/include/configs/sequoia.h
+++ b/include/configs/sequoia.h
@@ -37,6 +37,7 @@
 #else
 #define CONFIG_440GRX		1		/* Specific PPC440GRx	*/
 #endif
+#define CONFIG_440		1		/* ... PPC440 family	*/
 #define CONFIG_4xx		1		/* ... PPC4xx family	*/
 /* Detect Sequoia PLL input clock automatically via CPLD bit		*/
 #define CONFIG_SYS_CLK_FREQ    ((in8(CFG_BCSR_BASE + 3) & 0x80) ? \