Fix SBK-RAM Javadoc warnings

[kmgowda]

Describe the Issue (Bug/Feature)
Fix the Javadoc warning of sbk-ram module of SBK

To Reproduce
Just run : ./gradlew javadoc
you will get lots of javadoc warnings on sbk-api, sbk-ram, sbk-gem and sbk-gem-yal

Expected behavior
fix the warnings of sbk-ram module;
the command "./gradlew javadoc" should not yield any warnings on sbk-ram module/folder

Additional context
Fixing the Javadoc warning helps you to understand SBK framework internals

[kmgowda]

@Amartya-Mahato thank you