build: recovery: Remove INTERNAL_RECOVERY_FILES

INTERNAL_RECOVERY_FILES picks up all packages that install files into
TARGET_RECOVERY_OUT.  This is not necessarily desirable and circumvents
the normal PRODUCT_PACKAGES mechanism.

Change-Id: I66f38a6afed7ade19a50a321d3b2d197137ba3a7
Related: http://review.cyanogenmod.org/#/c/74243/
Show RECOVERY_VARIANT during dumpvar.mk if using alt recovery

Signed-off-by: dragon <dragon7780@hotmail.nl>