hw/i386: Move CONFIG_ACPI_PCI to CONFIG_PC

CONFIG_ACPI_PCI is a hard requirement of acpi-build.c, which is built
unconditionally for x86 target. Putting it in default-configs/ suggests
that it can be easily disabled, which isn't true.

Relocate the symbol with the other acpi-build.c requirements, under
'config PC'. This is similar to what is done for the arm 'virt' machine
type and CONFIG_ACPI_PCI

Signed-off-by: Cole Robinson <crobinso@redhat.com>
Message-Id: <e73e6edff68fd30d69c6a1d02c9ef9192f773c63.1568049871.git.crobinso@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>