ppc: Small change to CFG_MEM_TOP_HIDE description

Signed-off-by: Stefan Roese <sr@denx.de>

README

@@ -1936,9 +1936,9 @@ Configuration Settings:
 		fixing up gd->ram_size the Linux kernel should gets passed
 		the now "corrected" memory size and won't touch it either.
 		This should work for arch/ppc and arch/powerpc. Only Linux
-		board ports in arch/powerpc with bootwrapper support, that
+		board ports in arch/powerpc with bootwrapper support that
 		recalculate the memory size from the SDRAM controller setup
-		will have to get fixed.
+		will have to get fixed in Linux additionally.
 
 		This option can be used as a workaround for the 440EPx/GRx
 		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't