Revert "sh: Ensure fixmap and store queue space can co-exist."

Revert "sh: Ensure fixmap and store queue space can co-exist."

This reverts commit 7bf3f937169d9196be70d55a0c6efc92329a1525.
With store queues enabled the area above P4SEG has special properties
from the MMU's point of view, which was causing fixmap failure. We'll
have to do something else to satisfy the vmalloc range check.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>