New WIP port: Echo R1

The Echo R1 is a new open-hardware music player design, based
on the STM32H743 microcontroller. Schematics and hardware
documentation for it can be found here:

- https://github.com/amachronic/echoplayer

This is an incomplete port. The bootloader can be loaded using
OpenOCD and it can draw to the LCD using SPI. SDRAM is working
but hasn't been extensively tested.

Change-Id: Ifd2bee15c49868fbc989683d3ca14dce48bf3e18

firmware/export/config.h

@@ -84,6 +84,7 @@
 #define IMX233        233
 #define RK27XX       2700
 #define X1000        1000
+#define STM32H743   32743
 
 /* platforms
  * bit fields to allow PLATFORM_HOSTED to be OR'ed e.g. with a
@@ -163,6 +164,7 @@
 #define EROSQ_PAD          72
 #define FIIO_M3K_PAD       73
 #define SHANLING_Q1_PAD    74
+#define ECHO_R1_PAD        75
 
 /* CONFIG_REMOTE_KEYPAD */
 #define H100_REMOTE   1
@@ -282,6 +284,7 @@
 #define LCD_FIIOM3K       69 /* as used by the FiiO M3K */
 #define LCD_SHANLING_Q1   70 /* as used by the Shanling Q1 */
 #define LCD_EROSQ         71 /* as used by the ErosQ (native) */
+#define LCD_ECHO_R1       72 /* ILI9342, as used by the Echo R1 */
 
 /* LCD_PIXELFORMAT */
 #define HORIZONTAL_PACKING 1
@@ -359,6 +362,7 @@ Lyre prototype 1 */
 #define RTC_CONNECT  24 /* Sansa Connect AVR */
 #define RTC_NANO3G   25 /* Dialog Semiconductor D1671 ??? */
 #define RTC_NANO4G   26 /* Dialog Semiconductor D1759 ??? */
+#define RTC_STM32H743 27
 
 /* USB On-the-go */
 #define USBOTG_M66591   6591 /* M:Robe 500 */
@@ -610,6 +614,8 @@ Lyre prototype 1 */
 #include "config/shanlingq1.h"
 #elif defined(EROS_QN)
 #include "config/erosqnative.h"
+#elif defined(ECHO_R1)
+#include "config/echor1.h"
 #else
 //#error "unknown hwardware platform!"
 #endif