Update gensyscalls.sh not to generate an empty line at the end of the file

And then automatically update syscall_nr.h running scripts/gensyscalls.sh

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200930003033.554124-2-laurent@vivier.eu>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>