FUI: Fill in link_m and link_n values

... based on the EDID detailed timing values for
pixel_clock and link_clock.

Two undocumented registers 0x6f040 and 0x6f044 correspond to link_m and link_n
respectively.  Other two undocumented registers 0x6f030 and 0x6f034 correspond
to data_m and data_n respectively.

Calculations are based on the intel_link_compute_m_n from linux kernel.

Currently, the value for 0x6f030 does not come up right with our calculations.
Hence, set to hard-coded value.

Change-Id: I40ff411729d0a61759164c3c1098504973f9cf5e
Reviewed-on: https://gerrit.chromium.org/gerrit/62915
Reviewed-by: Ronald G. Minnich <rminnich@chromium.org>
Tested-by: Furquan Shaikh <furquan@chromium.org>
Commit-Queue: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: http://review.coreboot.org/4381
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

src/drivers/intel/gma/i915_reg.h

@@ -3321,6 +3321,10 @@
 #define _PIPEA_DATA_M1           0x60030
 #define  TU_SIZE(x)             (((x)-1) << 25) /* default size 64 */
 #define  TU_SIZE_MASK           0x7e000000
+
+#define  DATA_LINK_M_N_MASK     (0xffffff)
+#define  DATA_LINK_N_MAX        (0x800000)
+
 #define  PIPE_DATA_M1_OFFSET    0
 #define _PIPEA_DATA_N1           0x60034
 #define  PIPE_DATA_N1_OFFSET    0