openocd: remove command line flag -p/--pipe deprecated in v0.5.0

The OpenOCD command line flag -p/--pipe was marked as deprecated
in release v0.5.0, more than 9 years ago.
We can reasonably expect that in these 9 years any user of OpenOCD
has already migrated to v0.5.0 or to some newer release, thus has
already updated any local/personal script to get rid of the
deprecated message.

Drop the command line flag already deprecated in v0.5.0.

Change-Id: I2faeb592ed2c2f67c2d3227f118093e39fcf4a8c
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/6084


Tested-by: jenkins
Reviewed-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>