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

Logic and code for clearing PCI_EXP_LNKCTL_CLKREQ_EN bit is correct, but
comment describing it is misleading. PCI_EXP_LNKCTL_CLKREQ_EN bit should be
hardwired to zero but mvebu hw allows to change it.

Link: https://lore.kernel.org/r/20220104153529.31647-11-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>