config: Get rid of FAST_REBOOT_CLEARS_MEMORY

FAST_REBOOT_CLEARS_MEMORY is a relic of the initial attempts at fast
reboot, which went away in 0279d89 ("Fast reboot for P8").

Remove it from config.h as it's misleading.

Signed-off-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

include/config.h

@@ -72,9 +72,6 @@
  */
 //#define FORCE_DUMMY_CONSOLE 1
 
-/* Enable this to make fast reboot clear memory */
-//#define FAST_REBOOT_CLEARS_MEMORY	1
-
 /* Enable this to disable setting of the output pending event when
  * sending things on the console. The FSP is very slow to consume
  * and older kernels wait after each character during early boot so