flashing: introduce flash method 'esp32jtag' for esp32c3/esp32s3 targets

This adds a new flash method 'esp32jtag' to explicitly define when this
reset method is needed. When flashing esp32c3/esp32s3 boards on Windows
this method of board reset is required, otherwise the reset does not
take place and the board cannot be flashed.

Signed-off-by: deadprogram <ron@hybridgroup.com>

targets/esp32c3.json

@@ -13,7 +13,7 @@
 		"src/device/esp/esp32c3.S"
 	],
 	"binary-format": "esp32c3",
-	"flash-method": "esp32flash",
+	"flash-method": "esp32jtag",
 	"serial-port": ["303a:1001"],
 	"openocd-interface": "esp_usb_jtag",
 	"openocd-target": "esp32c3",

targets/esp32s3.json

@@ -15,7 +15,7 @@
 		"src/internal/task/task_stack_esp32.S"
 	],
 	"binary-format": "esp32s3",
-	"flash-method": "esp32flash",
+	"flash-method": "esp32jtag",
 	"emulator": "qemu-system-xtensa -machine esp32 -nographic -drive file={img},if=mtd,format=raw",
 	"gdb": ["xtensa-esp32-elf-gdb"]
 }