coreboot/fam15h: fix acpica build on newer hostcc

Changes made to acpica/iasl in crossgcc, for
coreboot trees fam15h_udimm and fam15h_rdimm:

remove superfluous YYSTYPE declaration

make LuxBuffer variables static, to avoid warnings
treated as errors about multiple definitions

AcpiGbl_DbOpt_NoRegionSupport - remove this definition
in source/tools/acpiexec/aemain.c because it's already
re-defined by acpiexec. otherwise the linker complains
about multiple definitions

Signed-off-by: Leah Rowe <leah@libreboot.org>