acpi/ghes: get rid of ACPI_HEST_SRC_ID_RESERVED

acpi/ghes: get rid of ACPI_HEST_SRC_ID_RESERVED

This is just duplicating ACPI_GHES_ERROR_SOURCE_COUNT, which
has a better name. So, drop the duplication.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <9012bf4c9630adf15a22af3c88fda8270916887b.1736945236.git.mchehab+huawei@kernel.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>