Replace unneeded manual dependency on header by adding it to SRCS.

bsd.lib.mk and bsd.prog.mk already depend all objs on headers in SRCS if
there is not yet a depend file. The headers in SRCS are never built or
installed. After 'make depend' the header was already added as a proper
dependency on the objects where needed.

MFC after: 2 weeks
Sponsored by: EMC / Isilon Storage Division