jtag: fix reset_config copy/paste error

As the other arg checks do not OR, it is assumed this is a copy/paste error
from the original code author.

Change-Id: I7dfc7396254a6f558887def951c57dfd4a0e6c2c
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/997
Tested-by: jenkins
Reviewed-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>

src/jtag/adapter.c

@@ -274,7 +274,7 @@ COMMAND_HANDLER(handle_reset_config_command)
 			goto next;
 
 		/* srst_type (NOP without HAS_SRST) */
-		m |= RESET_SRST_PUSH_PULL;
+		m = RESET_SRST_PUSH_PULL;
 		if (strcmp(*CMD_ARGV, "srst_push_pull") == 0)
 			tmp |= RESET_SRST_PUSH_PULL;
 		else if (strcmp(*CMD_ARGV, "srst_open_drain") == 0)