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/yosemite.h b/include/configs/yosemite.h
index b68ae54..c96b14e 100644
--- a/include/configs/yosemite.h
+++ b/include/configs/yosemite.h
@@ -38,6 +38,7 @@
 #define CONFIG_440GR		1	/* Specific PPC440GR support	*/
 #define CONFIG_HOSTNAME		yellowstone
 #endif
+#define CONFIG_440		1	/* ... PPC440 family		*/
 #define CONFIG_4xx		1	/* ... PPC4xx family		*/
 #define CONFIG_SYS_CLK_FREQ	66666666    /* external freq to pll	*/