linux-phytec-fsl

ARM: boot: Add an implementation of strnlen for libfdt

Recent versions of libfdt add a dependency on strnlen. Copy the
implementation in lib/string.c here, so we can update libfdt.

Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Rob Herring <robh@kernel.org>