imx-uuc: needs headers >= 3.18

The bump to 79e9798eee9cd972d92ed2b18f170de856d153c9 added the following
commit:
https://github.com/NXPmicro/imx-uuc/commit/ce808f3010ec73ccc07775c6cfd5317807a22415

This new ufb daemon uses usb_functionfs_descs_head_v2 which is available
only since 3.18:
https://github.com/torvalds/linux/commit/1df22b4ea9d91b01267fb61c155c31fb65d6b8a0

So add a dependency on headers >= 3.18

Fixes:
 - http://autobuild.buildroot.org/results/1081062b1c32c44a9feb5b14288095bc72d15986

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/freescale-imx/imx-uuc/Config.in

@@ -3,6 +3,7 @@ config BR2_PACKAGE_IMX_UUC
 	depends on BR2_TOOLCHAIN_HAS_THREADS
 	depends on BR2_arm # Only relevant for i.MX
 	depends on BR2_USE_MMU # fork()
+	depends on BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_18 # usb_functionfs_descs_head_v2
 	select BR2_PACKAGE_HOST_DOSFSTOOLS
 	help
 	  This package provides the Universal Adapter user-space
@@ -15,7 +16,8 @@ config BR2_PACKAGE_IMX_UUC
 	  This package is provided by Freescale/NXP as-is and doesn't
 	  have an upstream.
 
-comment "imx-uuc needs a toolchain w/ threads"
+comment "imx-uuc needs a toolchain w/ threads, headers >= 3.18"
 	depends on BR2_arm
 	depends on BR2_USE_MMU
-	depends on !BR2_TOOLCHAIN_HAS_THREADS
+	depends on !BR2_TOOLCHAIN_HAS_THREADS || \
+		!BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_18