Config.in.legacy: fix selection of firmware-imx

In order to select firmware-imx we have to select freescale-imx first.

Reported-by: Gary Bisson <gary.bisson@boundarydevices.com>
Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

Config.in.legacy

@@ -149,6 +149,7 @@ comment "Legacy options removed in 2021.02"
 config BR2_PACKAGE_LINUX_FIRMWARE_IMX_SDMA
 	bool "imx sdma firmware is provided by firmware-imx"
 	select BR2_LEGACY
+	select BR2_PACKAGE_FREESCALE_IMX
 	select BR2_PACKAGE_FIRMWARE_IMX
 	help
 	  linux-firmware provide the same firmware as firmware-imx.