Fixed board_id for Arduino Zero

boards.txt

@@ -10,7 +10,7 @@ arduino_zero_edbg.upload.native_usb=false
 arduino_zero_edbg.build.mcu=cortex-m0plus
 arduino_zero_edbg.build.f_cpu=48000000L
 arduino_zero_edbg.build.usb_product="Arduino Zero"
-arduino_zero_edbg.build.board=SAM_ZERO
+arduino_zero_edbg.build.board=SAMD_ZERO
 arduino_zero_edbg.build.core=arduino
 arduino_zero_edbg.build.extra_flags=-D__SAMD21G18A__ {build.usb_flags}
 arduino_zero_edbg.build.ldscript=linker_scripts/gcc/flash_with_bootloader.ld
@@ -34,7 +34,7 @@ arduino_zero_native.upload.native_usb=true
 arduino_zero_native.build.mcu=cortex-m0plus
 arduino_zero_native.build.f_cpu=48000000L
 arduino_zero_native.build.usb_product="Arduino Zero"
-arduino_zero_native.build.board=SAM_ZERO
+arduino_zero_native.build.board=SAMD_ZERO
 arduino_zero_native.build.core=arduino
 arduino_zero_native.build.extra_flags=-D__SAMD21G18A__ {build.usb_flags}
 arduino_zero_native.build.ldscript=linker_scripts/gcc/flash_with_bootloader.ld