Add GD25Q64C as a flash chip for Sol

Author: theacodes

ports/atmel-samd/boards/winterbloom_sol/mpconfigboard.mk

@@ -12,8 +12,8 @@ CHIP_VARIANT = SAMD51J20A
 CHIP_FAMILY = samd51
 
 QSPI_FLASH_FILESYSTEM = 1
-EXTERNAL_FLASH_DEVICE_COUNT = 1
-EXTERNAL_FLASH_DEVICES = W25Q32JV_IQ
+EXTERNAL_FLASH_DEVICE_COUNT = 2
+EXTERNAL_FLASH_DEVICES = "GD25Q64C, W25Q32JV_IQ"
 LONGINT_IMPL = MPZ
 
 # Disable modules that are unusable on this special-purpose board.