tuna: remove recovery_keys.c

No longer needed because of changes to default_recovery_keys.c

See http://review.cyanogenmod.org/#/c/62724

Change-Id: I7e43ab5b14e47f4839a5072bedf56e4c9a8fab78
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_device_samsung_tuna into HEAD