acpi_spmc(4): Constraints: Rename the Intel-format parser

...from acpi_spmc_get_constraints_spec() to
acpi_spmc_get_constraints_intel(), as really there is no ACPI
specification proper and parsing the constraints is done according to
some *Intel* specification (even if it is true that, by contrast, AMD
has none).

No functional change (intended).

Reviewed by: obiwac, imp
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D56800