PCI: endpoint: Allow only_64bit on BAR_RESERVED

PCI: endpoint: Allow only_64bit on BAR_RESERVED

Remove the documentation that forbids setting only_64bit on a BAR of type
BAR_RESERVED.

When a reserved BAR is 64-bit by default, setting only_64bit is the most
accurate description. If we later add support to disable a reserved BAR
(e.g. disable_bar() for BARs that were never set via set_bar()), the
implementation will need to clear the adjacent BAR (upper 32 bits) as well;
having only_64bit set documents that requirement.

Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20260312130229.2282001-14-cassel@kernel.org