mmc: fsl_esdhc: Add adapter card type identification support

Add adapter card type identification support by reading
FPGA STAT_PRES1 register SDHC Card ID[0:2] bits. To use this function,
define CONFIG_FSL_ESDHC_ADAPTER_IDENT.

Signed-off-by: Yangbo Lu <yangbo.lu@freescale.com>
Cc: York Sun <yorksun@freescale.com>
Cc: Pantelis Antoniou <panto@antoniou-consulting.com>
[York Sun: resolve conflicts in README.fsl-esdhc]
Reviewed-by: York Sun <yorksun@freescale.com>
diff --git a/doc/README.fsl-esdhc b/doc/README.fsl-esdhc
index 619c6b2..7e71387 100644
--- a/doc/README.fsl-esdhc
+++ b/doc/README.fsl-esdhc
@@ -1,6 +1,24 @@
-CONFIG_SYS_FSL_ESDHC_LE means ESDHC IP is in little-endian mode.
-CONFIG_SYS_FSL_ESDHC_BE means ESDHC IP is in big-endian mode.
-CONFIG_SYS_FSL_ESDHC_FORCE_VSELECT forces to run at 1.8V.
+Freescale esdhc-specific options
 
-Accessing ESDHC registers can be determined by ESDHC IP's endian
-mode or processor's endian mode.
+	- CONFIG_FSL_ESDHC_ADAPTER_IDENT
+		Support Freescale adapter card type identification. This is implemented by
+		operating Qixis FPGA relevant registers. The STAT_PRES1 register has SDHC
+		Card ID[0:2] bits showing the type of card installed in the SDHC Adapter Slot.
+
+		SDHC Card ID[0:2]	Adapter Card Type
+		0b000			reserved
+		0b001			eMMC Card Rev4.5
+		0b010			SD/MMC Legacy Card
+		0b011			eMMC Card Rev4.4
+		0b100			reserved
+		0b101			MMC Card
+		0b110			SD Card Rev2.0/3.0
+		0b111			No card is present
+	- CONFIG_SYS_FSL_ESDHC_LE
+		ESDHC IP is in little-endian mode. Accessing ESDHC registers can be
+		determined by ESDHC IP's endian mode or processor's endian mode.
+	- CONFIG_SYS_FSL_ESDHC_BE
+		ESDHC IP is in big-endian mode. Accessing ESDHC registers can be determined
+		by ESDHC IP's endian mode or processor's endian mode.
+
+	- CONFIG_SYS_FSL_ESDHC_FORCE_VSELECT forces to run at 1.8V.