85xx: Using proper I2C source clock divider for MPC8544

The MPC8544 RM incorrect shows the SEC_CFG bit in PORDEVSR2 as being
bit 26, instead it should be bit 28.  This caused in incorrect
interpretation of the i2c_clk which is the same as the SEC clk on
MPC8544.  The SEC clk is controlled by cfg_sec_freq that is reported
in PORDEVSR2.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

include/asm-ppc/immap_85xx.h

@@ -1579,7 +1579,7 @@ typedef struct ccsr_gur {
 #define MPC85xx_PORDEVSR_RIO_DEV_ID	0x00000007
 	uint	pordbgmsr;	/* 0xe0010 - POR debug mode status register */
 	uint	pordevsr2;	/* 0xe0014 - POR I/O device status regsiter 2 */
-#define MPC85xx_PORDEVSR2_SEC_CFG	0x00000020
+#define MPC85xx_PORDEVSR2_SEC_CFG	0x00000080
 	char	res1[8];
 	uint	gpporcr;	/* 0xe0020 - General-purpose POR configuration register */
 	char	res2[12];