[ELF][ARM] Increase default max-page-size from 4096 to 6536

See http://lists.llvm.org/pipermail/llvm-dev/2020-April/140549.html

For the record, GNU ld changed to 64k max page size in 2014
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=7572ca8989ead4c3425a1500bc241eaaeffa2c89
"[RFC] ld/ARM: Increase maximum page size to 64kB"

Android driver forced 4k page size in AArch64 (D55029) and ARM (D77746).

A binary linked with max-page-size=4096 does not run on a system with a
higher page size configured. There are some systems out there that do
this and it leads to the binary getting `Killed!` by the kernel.

In the non-linker-script cases, when linked with -z noseparate-code
(default), the max-page-size increase should not cause any size
difference. There may be some VMA usage differences, though.

Reviewed By: psmith, MaskRay

Differential Revision: https://reviews.llvm.org/D77330