coding style: avoid unnecessary line continuations

coding style: avoid unnecessary line continuations

Line continuation, adding a backslash as last char of the line, is
requested in multi-line macro definition, but is not necessary in
the rest of C code.

Remove it where present.

Identified by checkpatch script from Linux kernel v5.1 using the
command

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

Change-Id: Id0c69e93456731717a7b290b16580e9f8ae741bc
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5619
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Tested-by: jenkins