scripts: add a script to generate syscall_nr.h

This script is needed for targets based on asm-generic syscall numbers generation

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200316085620.309769-2-laurent@vivier.eu>
[lv: added file in MAINTAINERS]
2 files changed