PCI: mvebu: Update comment for PCI_EXP_LNKCAP register on emulated bridge

Reason for clearing this bit is because mvebu hw returns incorrectly this bit set to 1.

Link: https://lore.kernel.org/r/20220104153529.31647-10-pali@kernel.org


Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>