Revert "arm64: virt: ensure visibility of __boot_cpu_mode"

This reverts commit 82b2f495fba338d1e3098dde1df54944a9c19751. The
__boot_cpu_mode variable is flushed in head.S after being written,
therefore the additional cache flushing is no longer required.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Git-commit: 0a997ecc08e0b551119c56d52a591d9e5b38a7cd
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>