x86, bios: Make the x86 early memory reservation a kernel option

Add a kernel command-line option so the x86 early memory reservation
size can be adjusted at runtime instead of only at compile time.

Suggested-by: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <tip-d0cd7425fab774a480cce17c2f649984312d0b55@git.kernel.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 683ae8f..d359000 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1326,7 +1326,7 @@
 	  Set whether the default state of memory_corruption_check is
 	  on or off.
 
-config X86_LOW_RESERVE
+config X86_RESERVE_LOW
 	int "Amount of low memory, in kilobytes, to reserve for the BIOS"
 	default 64
 	range 4 640