Change in coreboot[master]: src: add IS_ENABLED() around Kconfig symbol references

[build bot (Jenkins) (Code Review)]

build bot (Jenkins) has posted comments on this change. ( https://review.coreboot.org/20358 )

Change subject: src: add IS_ENABLED() around Kconfig symbol references
......................................................................

Patch Set 1: Verified+1

Build Successful

https://qa.coreboot.org/job/coreboot-gerrit/56171/ : SUCCESS

https://qa.coreboot.org/job/coreboot-checkpatch/11774/ : SUCCESS