coding style: prototype of functions with no parameters

coding style: prototype of functions with no parameters

Functions that have no parameters should use "void" as parameter
in the function declaration.

Issue identified and fixed by script checkpatch from Linux kernel
v5.1 using the command

	find src/ -type f -exec ./tools/scripts/checkpatch.pl \
	-q --types FUNCTION_WITHOUT_ARGS --fix-inplace -f {} \;

Change-Id: If104ac75b44e939ec86155ff7b5720f2e33c6b39
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5621
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Tested-by: jenkins