arm: mx6: tqma6: fix build for WRU-IV baseboard

Fix:
 undefined reference to `spi_flash_free'
 undefined reference to `spi_flash_probe'

Signed-off-by: Stefano Babic <sbabic@denx.de>
CC: Stefan Roese <sr@denx.de>
Cc: Markus Niebel <Markus.Niebel@tq-group.com>
Acked-by: Stefan Roese <sr@denx.de>

configs/tqma6s_wru4_mmc_defconfig

@@ -10,3 +10,4 @@ CONFIG_AUTOBOOT_PROMPT="Enter password in %d seconds to stop autoboot\n"
 CONFIG_AUTOBOOT_ENCRYPTION=y
 CONFIG_AUTOBOOT_STOP_STR_SHA256="36a9e7f1c95b82ffb99743e0c5c4ce95d83c9a430aac59f84ef3cbfab6145068"
 CONFIG_PCA9551_LED=y
+CONFIG_SPI_FLASH=y