fsl-layerscape: drop obsolete PPA secure firmware support

PPA was a secure firmware developed in-house which is no longer
supported and replaced by TF-A quite some years ago. Drop support
for it.

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/env/Kconfig b/env/Kconfig
index 54203fa..67b819d 100644
--- a/env/Kconfig
+++ b/env/Kconfig
@@ -645,7 +645,7 @@
 
 config SYS_MMC_ENV_DEV
 	int "mmc device number"
-	depends on ENV_IS_IN_MMC || ENV_IS_IN_FAT || SYS_LS_PPA_FW_IN_MMC || \
+	depends on ENV_IS_IN_MMC || ENV_IS_IN_FAT || \
 		CMD_MVEBU_BUBT || FMAN_ENET || QE || PHY_CORTINA
 	default 0
 	help