package/openocd: fix indentation of Config.in help text

Fixes the following check-package warnings:

package/openocd/Config.in:20: help text: <tab><2 spaces><62 chars> (http://nightly.buildroot.org/#writing-rules-config-in)
package/openocd/Config.in:21: help text: <tab><2 spaces><62 chars> (http://nightly.buildroot.org/#writing-rules-config-in

)

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>