disp/nv50: Add method for probing active heads
nv50/display: Set VBLANK time in modeset script

Solves blinking on reclocking memory. The value set is an underestimate, but better than nothing
pwr/memx/nva3: Implement "wait for VBLANK"
pwr/memx: Make FB disable and enable explicit

Needs to be done after wait-for-VBLANK, and NVA3 requires register writes in between. Rather than hard-coding register writes, just split out fb_disable and fb_enable.
fb/ramnve0: Disable FB before reclocking

This used to be done implicitly
pwr/memx: Return execution time
pwr/memx: Match blobs behaviour
fb/ramnv50: Store the number of partitions in the designated fields
bios/ramtrain: Parse ram training table basics
fb/ramnva3: WIP link training unit

XXX: Multiple partitions
fb/ramnva3: Use ram->base structs instead of local structs

This will ease the use of generic timing and MR generation bits later
fb/ramnva3: Ressurect timing calculation code
fb/sddr3: Expand MR generation with various bits
fb/sddr2: Generate MR values
fb/nva3: WIP Start on some reclocking bits
WIP train external hook
fb/ramnva3: WIP support for DDR2 reclocking
fb/ramfuc: Support strided regs
fb/ramnva3: WIP Per-partition regs
fb/ramnva3: Initialise PART_PM_SEL