lib: stdbool header from the FreeBSD project
lib: stdbool header from the FreeBSD project

This patch pulls the stdbool.h header file from the FreeBSD
project. The platforms require this header to fix many MISRA
defects among other things.

Signed-off-by: Varun Wadekar <517ae08f01cae398dbba5bef5ba1750f384c6daf@nvidia.com>

lsigithub/arm-trusted-firmware_public,achingupta/arm-trusted-firmware,lsigithub/arm-trusted-firmware_public,achingupta/arm-trusted-firmware