Address various issues raised by TinyUSB maintainers

- remove OPT_MCU_SAME51 in favor of OPT_MCU_SAME5X and working around
  differences in the Atmel bsp locally in the D5035-01 bsp.

- rename board folder to d5035_01 for consistency with other boards

hw/bsp/d5035_01/board.mk

@@ -0,0 +1,63 @@
+CFLAGS += \
+  -mthumb \
+  -mabi=aapcs \
+  -mlong-calls \
+  -mcpu=cortex-m4 \
+  -mfloat-abi=hard \
+  -mfpu=fpv4-sp-d16 \
+  -nostdlib -nostartfiles \
+  -D__SAME51J19A__ \
+  -DCONF_CPU_FREQUENCY=80000000 \
+  -DCONF_GCLK_USB_FREQUENCY=48000000 \
+  -DCFG_TUSB_MCU=OPT_MCU_SAME5X \
+  -DD5035_01=1 \
+  -DBOARD_NAME="\"D5035-01\"" \
+  -DSVC_Handler=SVCall_Handler
+
+HWRED ?= 1
+
+CFLAGS += -DHWREV=$(HWREV)
+
+
+# All source paths should be relative to the top level.
+LD_FILE = hw/bsp/$(BOARD)/same51j19a_flash.ld
+
+SRC_C += \
+	hw/mcu/microchip/same51/gcc/gcc/startup_same51.c \
+  hw/mcu/microchip/same51/gcc/system_same51.c \
+
+ifdef SYSCALLS
+ifneq ($(SYSCALLS),0)
+  SRC_C += hw/mcu/microchip/same51/hal/utils/src/utils_syscalls.c
+endif
+endif
+
+ifdef LOG
+ifneq ($(LOG),0)
+  SRC_C += hw/mcu/microchip/same51/hal/utils/src/utils_syscalls.c
+endif
+endif
+
+INC += \
+	$(TOP)/hw/mcu/microchip/same51/ \
+	$(TOP)/hw/mcu/microchip/same51/config \
+	$(TOP)/hw/mcu/microchip/same51/include \
+	$(TOP)/hw/mcu/microchip/same51/hal/include \
+	$(TOP)/hw/mcu/microchip/same51/hal/utils/include \
+	$(TOP)/hw/mcu/microchip/same51/hpl/port \
+	$(TOP)/hw/mcu/microchip/same51/hri \
+	$(TOP)/hw/mcu/microchip/same51/CMSIS/Core/Include
+
+# For TinyUSB port source
+VENDOR = microchip
+CHIP_FAMILY = samd
+
+# For freeRTOS port source
+FREERTOS_PORT = ARM_CM4F
+
+# For flash-jlink target
+JLINK_DEVICE = ATSAME51J19
+JLINK_IF = swd
+
+# flash using jlink
+flash: flash-jlink