Move SDCard SPI clock dividers into target.h (they depend on the bus Hz)

src/main/drivers/sdcard.c

@@ -1181,7 +1181,7 @@ static bool sdcard_completeInit()
         DESELECT_SDCARD;
     }
 
-    spiSetDivisor(SDCARD_SPI_INSTANCE, 4);
+    spiSetDivisor(SDCARD_SPI_INSTANCE, SDCARD_SPI_FULL_SPEED_CLOCK_DIVIDER);
 
     sdcard.state = SDCARD_STATE_READY;
 
@@ -1211,7 +1211,7 @@ static bool sdcard_checkInitDone() {
 bool sdcard_init()
 {
     // Max frequency is initially 400kHz
-    spiSetDivisor(SDCARD_SPI_INSTANCE, 128);
+    spiSetDivisor(SDCARD_SPI_INSTANCE, SDCARD_SPI_INITIALIZATION_CLOCK_DIVIDER);
 
     // SDCard wants 1ms minimum delay after power is applied to it
     delay(1000);

src/main/target/STM32F3DISCOVERY/target.h

@@ -100,6 +100,10 @@
 #define SDCARD_SPI_CS_GPIO                GPIOB
 #define SDCARD_SPI_CS_PIN                 GPIO_Pin_12
 #define SDCARD_SPI_CS_GPIO_CLK_PERIPHERAL RCC_APB2Periph_GPIOB
+// SPI2 is on the APB1 bus whose clock runs at 36MHz. Divide to under 400kHz for init:
+#define SDCARD_SPI_INITIALIZATION_CLOCK_DIVIDER 128
+// Divide to under 25MHz for normal operation:
+#define SDCARD_SPI_FULL_SPEED_CLOCK_DIVIDER 2
 
 #define ACC
 #define USE_ACC_LSM303DLHC