fmc: fmlib needs a linux kernel, so propagate dependency

At the same time fixup the comments to only be visible if we are
on a suitable arch.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/fmc/Config.in

@@ -1,10 +1,16 @@
 comment "fmc needs a toolchain w/ C++"
+	depends on BR2_powerpc_e500mc
 	depends on !BR2_INSTALL_LIBSTDCPP
 
+comment "fmc needs a Linux kernel to be built"
+	depends on BR2_powerpc_e500mc
+	depends on !BR2_LINUX_KERNEL
+
 config BR2_PACKAGE_FMC
 	bool "fmc"
 	depends on BR2_powerpc_e500mc
 	depends on BR2_INSTALL_LIBSTDCPP
+	depends on BR2_LINUX_KERNEL # fmlib
 	select BR2_PACKAGE_TCLAP
 	select BR2_PACKAGE_LIBXML2
 	select BR2_PACKAGE_FMLIB