[coreboot] MAKEFLAGS += -rR in buildrom

[Jordan Crouse]

Uwe, and others - why are we passing -rR into MAKEFLAGS in buildrom?
This completely hoses packages that otherwise use implicit rules
(such as memtest).  I assume this was added for Kconfig, but if there 
isn't a really compelling reason to use it, we should pull it out.

Jordan