PCI: Update CXL DVSEC definitions

PCI: Update CXL DVSEC definitions

CXL DVSEC definitions were recently moved into uapi/pci_regs.h, but the
newly added macros do not follow the file's existing naming conventions.
The current format uses CXL_DVSEC_XYZ, while the new CXL entries must
instead use the PCI_DVSEC_CXL_XYZ prefix to match the conventions already
established in pci_regs.h.

The new CXL DVSEC macros also introduce _MASK and _OFFSET suffixes, which
are not used anywhere else in the file. These suffixes lengthen the
identifiers and reduce readability. Remove _MASK and _OFFSET from the
recently added definitions.

Additionally, remove PCI_DVSEC_HEADER1_LENGTH, as it duplicates the existing
PCI_DVSEC_HEADER1_LEN() macro.

Update all existing references to use the new macro names.

Finally, update the inline documentation to reference the latest revision
of the CXL specification.

Signed-off-by: Terry Bowman <terry.bowman@amd.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20260114182055.46029-3-terry.bowman@amd.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>