Merge patch series "memtest performance improvements"

Rasmus Villemoes <ravi@prevas.dk> says:

The first two patches make memtest run ~40x faster (when, as it should
be, dcache is disabled), with the second patch being responsible for
most of that. At least on the beagleboneblack which I used for
testing; other boards and configurations will likely see different
numbers.

This is for CONFIG_SYS_ALT_MEMTEST=y and
CONFIG_SYS_ALT_MEMTEST_BITFLIP=n; one could probably get a similar
improvement in the bitflip case since that also has a schedule() call
in the inner loop.

Link: https://lore.kernel.org/r/20250822181848.3325832-1-ravi@prevas.dk