Allow to redefine hardware flow control

By default, it is disabled.
It could be redefined in variant.h adding:
If SDMMC:
#define SD_HW_FLOW_CTRL SDMMC_HARDWARE_FLOW_CONTROL_ENABLE
if SDIO:
#define SD_HW_FLOW_CTRL SDIO_HARDWARE_FLOW_CONTROL_ENABLE

or using build_opt.h:
If SDMMC:
-DSD_HW_FLOW_CTRL=SDMMC_HARDWARE_FLOW_CONTROL_ENABLE
if SDIO:
-DSD_HW_FLOW_CTRL=SDIO_HARDWARE_FLOW_CONTROL_ENABLE

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

src/bsp_sd.c

@@ -91,7 +91,9 @@
 #define SD_CLK_PWR_SAVE        SDMMC_CLOCK_POWER_SAVE_DISABLE
 #define SD_BUS_WIDE_1B         SDMMC_BUS_WIDE_1B
 #define SD_BUS_WIDE_4B         SDMMC_BUS_WIDE_4B
+#ifndef SD_HW_FLOW_CTRL
 #define SD_HW_FLOW_CTRL        SDMMC_HARDWARE_FLOW_CONTROL_DISABLE
+#endif
 #define SD_CLK_DIV             SDMMC_TRANSFER_CLK_DIV
 /* Definition for MSP SD */
 #define SD_AF                  GPIO_AF12_SDMMC1
@@ -105,7 +107,9 @@
 #define SD_CLK_PWR_SAVE        SDIO_CLOCK_POWER_SAVE_DISABLE
 #define SD_BUS_WIDE_1B         SDIO_BUS_WIDE_1B
 #define SD_BUS_WIDE_4B         SDIO_BUS_WIDE_4B
+#ifndef SD_HW_FLOW_CTRL
 #define SD_HW_FLOW_CTRL        SDIO_HARDWARE_FLOW_CONTROL_DISABLE
+#endif
 #define SD_CLK_DIV             SDIO_TRANSFER_CLK_DIV
 /* Definition for MSP SD */
 #define SD_AF                  GPIO_AF12_SDIO