ARM: 8318/1: treat CPU feature register fields as signed quantities

The various CPU feature registers consist of 4-bit blocks that
represent signed quantities, whose positive values represent
incremental features, and whose negative values are reserved.

To improve forward compatibility, update the feature detection
code to take possible future higher values into account, but
ignore negative values.

Change-Id: I7f1de53f80f2319dd6170beb4d119d5f4f2232bb
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Git-commit: b8c9592b4a6c93211c8163888a97880d608503b5
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>