x1000: rewrite SD driver using sdmmc_host

Remove all SD protocol handling and all target specific code
like GPIO/interrupt handling and clock parent setup. This can
now be handled from sdmmc_host_target_init() for each target.

Now only the clock frequency is managed by the MSC driver.
To make this code easier to factor out later, it's confined
to helper functions that do not access the driver state.

One small change is that MSCxDIV output is now clamped to a
minimum of 50MHz to avoid unnecessary frequency changes. The
MSC_CLKRT divider can still divide 50MHz down to 400 KHz so
there is no downside to this.

Auto-CMD12 is now unused. Using it would make error handling
more difficult for sdmmc_host since the controller does not
expose response data for the auto-CMD12.

Explicit CMD12 was not handled correctly in the old version
of the driver because the busy signal was ignored for R1b
responses if there was no associated data transfer. This is
now fixed by waiting for the PRG_DONE interrupt instead of
END_CMD_RES for non-data transfer R1b type commands.

Since existing X1000 targets are all very similar they use
a shared implementation in sdmmc-x1000-common.c for clock
setup and card detection. New targets can either use this
or create a separate file if they are different enough to
warrant one.

Change-Id: I35396637325d7c06a10151bb6aee64cabdc7b682

firmware/export/config/erosqnative.h

@@ -95,6 +95,9 @@
 #define STORAGE_WANTS_ALIGN
 #define STORAGE_NEEDS_BOUNCE_BUFFER
 
+/* One SD card slot */
+#define SDMMC_HOST_NUM_SD_CONTROLLERS 1
+
 /* Power management */
 #define CONFIG_BATTERY_MEASURE (VOLTAGE_MEASURE | PERCENTAGE_MEASURE/*|CURRENT_MEASURE*/)
 #define CONFIG_CHARGING        CHARGING_MONITOR

firmware/export/config/fiiom3k.h

@@ -84,6 +84,9 @@
 #define STORAGE_WANTS_ALIGN
 #define STORAGE_NEEDS_BOUNCE_BUFFER
 
+/* One SD card slot */
+#define SDMMC_HOST_NUM_SD_CONTROLLERS 1
+
 /* RTC settings */
 #define CONFIG_RTC      RTC_X1000
 /* TODO: implement HAVE_RTC_ALARM */

firmware/export/config/shanlingq1.h

@@ -67,6 +67,9 @@
 #define STORAGE_WANTS_ALIGN
 #define STORAGE_NEEDS_BOUNCE_BUFFER
 
+/* One SD card slot */
+#define SDMMC_HOST_NUM_SD_CONTROLLERS 1
+
 /* RTC settings */
 #define CONFIG_RTC      RTC_X1000
 /* TODO: implement HAVE_RTC_ALARM */