PCI/PTM: Preserve RsvdP bits in PTM Control register

Even though only the low 16 bits of PTM Control are currently defined, the
register is 32 bits wide and the unused bits are RsvdP ("Reserved and
Preserved"), so software must preserve the values of those bits when
writing the register.

Update PTM Control reads and writes to use 32-bit accesses and preserve the
reserved bits on writes.

Link: https://lore.kernel.org/r/20220909202505.314195-7-helgaas@kernel.org


Tested-by: Rajvi Jingar <rajvi.jingar@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>