Since requests for enabling or disabling interrupt lines can now
operate in sync mode, there is no point in keeping the post_ hint into
the names of the corresponding routines.

udd_post_irq_enable => udd_enable_irq
udd_post_irq_disable => udd_disable_irq

In addition, those services now go through the RTDM layer for applying
the requested change, instead of taking sideways by calling the I-pipe
API directly, which is wrong (we shall NOT bypass
xnintr_enable/disable due to locking requirements in the Cobalt core).