fsl: layerscape: guard *env_sf_get_env_addr() on CONFIG_ENV_IS_IN_SPI_FLASH

These functions can only be built and used when we have
ENV_IS_IN_SPI_FLASH, use that as a guard.

Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/board/freescale/ls1088a/ls1088a.c b/board/freescale/ls1088a/ls1088a.c
index f159298..4ecf6dc 100644
--- a/board/freescale/ls1088a/ls1088a.c
+++ b/board/freescale/ls1088a/ls1088a.c
@@ -1008,8 +1008,10 @@
 }
 #endif
 
+#ifdef CONFIG_ENV_IS_IN_SPI_FLASH
 void *env_sf_get_env_addr(void)
 {
 	return (void *)(CONFIG_SYS_FSL_QSPI_BASE + CONFIG_ENV_OFFSET);
 }
 #endif
+#endif