Better defaults, compatibility for SDIO + STM32 (#20570)

platformio.ini

@@ -973,7 +973,7 @@ board_build.offset   = 0x7000
 board_build.encrypt  = Yes
 board_build.firmware = Robin.bin
 build_flags          = ${common_stm32.build_flags}
-  -DENABLE_HWSERIAL3 -DTRANSFER_CLOCK_DIV=8 -DTIMER_SERIAL=TIM5
+  -DENABLE_HWSERIAL3 -DTIMER_SERIAL=TIM5
 build_unflags        = ${common_stm32.build_unflags}
  -DUSBCON -DUSBD_USE_CDC
 extra_scripts        = ${common.extra_scripts}
@@ -1149,7 +1149,7 @@ upload_protocol = jlink
 [env:flsun_hispeedv1]
 platform             = ${common_stm32.platform}
 extends              = common_stm32
-build_flags          = ${common_stm32.build_flags} -DMCU_STM32F103VE -DSS_TIMER=4 -DENABLE_HWSERIAL3 -DTRANSFER_CLOCK_DIV=8
+build_flags          = ${common_stm32.build_flags} -DMCU_STM32F103VE -DSS_TIMER=4 -DENABLE_HWSERIAL3
 board                = genericSTM32F103VE
 board_build.core     = stm32
 board_build.variant  = MARLIN_F103Vx
@@ -1321,7 +1321,7 @@ extra_scripts       = ${common.extra_scripts}
 build_flags         = ${common_stm32.build_flags}
   -DSTM32F4 -DSTM32F4xx -DTARGET_STM32F4
   -DDISABLE_GENERIC_SERIALUSB -DARDUINO_ARCH_STM32 -DARDUINO_LERDGE
-  -DTRANSFER_CLOCK_DIV=8 -DHAL_SRAM_MODULE_ENABLED
+  -DHAL_SRAM_MODULE_ENABLED
 build_unflags       = ${common_stm32.build_unflags} -DUSBCON -DUSBD_USE_CDC -DUSBD_VID=0x0483
 
 #
@@ -1369,7 +1369,7 @@ monitor_speed   = 500000
 [env:mks_robin_nano35_stm32]
 platform             = ${common_stm32.platform}
 extends              = common_stm32
-build_flags          = ${common_stm32.build_flags} -DMCU_STM32F103VE -DSS_TIMER=4 -DENABLE_HWSERIAL3 -DTRANSFER_CLOCK_DIV=8
+build_flags          = ${common_stm32.build_flags} -DMCU_STM32F103VE -DSS_TIMER=4 -DENABLE_HWSERIAL3
 board                = genericSTM32F103VE
 board_build.core     = stm32
 board_build.variant  = MARLIN_F103Vx