spl: Ensure all SPL symbols in Kconfig have some SPL dependency

Tighten up symbol dependencies in a number of places.  Ensure that a SPL
specific option has at least a direct dependency on SPL.  In places
where it's clear that we depend on something more specific, use that
dependency instead.  This means in a very small number of places we can
drop redundant dependencies.

Reported-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/fs/cbfs/Kconfig b/fs/cbfs/Kconfig
index 03980d8..b663992 100644
--- a/fs/cbfs/Kconfig
+++ b/fs/cbfs/Kconfig
@@ -9,6 +9,7 @@
 
 config SPL_FS_CBFS
 	bool "Enable CBFS (Coreboot Filesystem) in SPL"
+	depends on SPL
 	help
 	  Define this to enable support for reading from a Coreboot
 	  filesystem. This is a ROM-based filesystem used for accessing files