Based on the platform, Bspec expects us to wait or poll with
timeout for DDI BUF IDLE bit to be set to 0 (non idle) or get active
after enabling DDI_BUF_CTL.

v2:
* Based on platform, fixed delay or poll (Ville)
* Use a helper to do this (Imre, Ville)
v3:
* Add a new function _active for DDI BUF CTL to be non idle (Ville)
v4:
* Use the timeout for GLK (Ville)
v5:
* Add bspec quote, change timeout to 500us (Ville)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200701221052.8946-2-manasi.d.navare@intel.com