src/cpu: Remove dead sourced lines

Change-Id: I836ff09da17373d47daf21c98e5ab975836cd47e
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/29584
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>

src/cpu/amd/agesa/Kconfig

@@ -80,6 +80,5 @@ endif # CPU_AMD_AGESA
 
 source src/cpu/amd/agesa/family12/Kconfig
 source src/cpu/amd/agesa/family14/Kconfig
-source src/cpu/amd/agesa/family15/Kconfig
 source src/cpu/amd/agesa/family15tn/Kconfig
 source src/cpu/amd/agesa/family16kb/Kconfig