The kernel takes a very long time to boot if the memory size is bigger then
32767 MB.  The memory size is contained in a structure created by an sclp
call.  The kernel accesses the field with a LH instrution which performs a
sign extension of a 16 bit word.  In the case of a memory size with bit 2^15
set this results in a very large value and the memory detection just loops for
a long time.  In addition if more then 64 GB are used on a 64 bit system the
memory size is read from an incorrect storage location.

Use zero-extention to read the 16 bit memory size and the correct offset to
read the 4 byte memory size on 64 bit.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>