boundary: common: mx6: 800mhz_256mx16: increase tRFC

nw2 seems to need this change. Data sheet says 104 ns. This
is a little more.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>

board/boundary/common/mx6/800mhz_256mx16.cfg

@@ -56,14 +56,14 @@
 DATA 4, MX6_MMDC_P0_MDPDC, 0x0002002d
 DATA 4, MX6_MMDC_P0_MDSCR, 0x00008000
 /*
- * tRFC:0x66		(260000/2525) = 102.97 = 103(0x67) clocks
+ * tRFC:0x69		(267000/2525) = 105.74 = 106(0x6a) clocks
  * tXS:0x6a		(270000/2525) = 106.93 = 107(0x6b) clocks
  * tXP:b'010'		(6000/2525) = 2.376 = 3 clocks
  * tXPDLL:b'1001'	(24000/2525) = 9.505 = 10(0x0a) clocks
  * tFAW:b'10011'	(50000/2525) = 19.802 = 20(0x14) clocks
  * tCL:b'0011'		(13125/2525) = 5.198 = 6 clocks
  */
-DATA 4, MX6_MMDC_P0_MDCFG0, 0x666a5333
+DATA 4, MX6_MMDC_P0_MDCFG0, 0x696a5333
 /*
  * tRCD:b'101'		(13125/2525) = 5.198 = 6 clocks
  * tRP:b'101'		(13125/2525) = 5.198 = 6 clocks