s390: avoid z13 cache aliasing

Avoid cache aliasing on z13 by aligning shared objects to multiples
of 512K. The virtual addresses of a page from a shared file needs
to have identical bits in the range 2^12 to 2^18.

Change-Id: I5dc15ba77d19bd9f95cd731206406387c5e30131
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Git-commit: 1f6b83e5e4d3aed46eac1d219322fba9c7341cd8
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Se Wang (Patrick) Oh <sewango@codeaurora.org>