OpenULINK firmware: Use C99 designated struct initializers

OpenULINK firmware: Use C99 designated struct initializers

Recent versions of SDCC added support for C99 designated struct initializers.
This provides better code readability (no functional changes).

Successfully tested with ULINK probe and STM32F103 (debug, erase and write
flash).

Change-Id: Idfa35147d2c3043baaa21a811b926b3845c85f9b
Signed-off-by: Martin Schmölzer <martin.schmoelzer@student.tuwien.ac.at>
Reviewed-on: http://openocd.zylin.com/1484
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>