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

src/rtos/linux.c

@@ -1379,8 +1379,8 @@ static int linux_thread_packet(struct connection *connection, char const *packet
 						 target->rtos->
 						 current_threadid)
 				&& (target->rtos->current_threadid != -1))
-					LOG_WARNING("WARNING! current GDB thread do not match" \
-							"current thread running." \
+					LOG_WARNING("WARNING! current GDB thread do not match"
+							"current thread running."
 							"Switch thread in GDB to threadid %d",
 							(int)ct->threadid);