kconfig: Make zconf.y work with current bison

zconf.y includes zconf.hash.c from the initial code section.
zconf.hash.c references the token constants from zconf.y.  However,
current bison defines the token constants after the initial code
section, making zconf.hash.c fail to compile.  Move the include of
zconf.hash.c later in zconf.y, so bison puts it after the token
constants.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>