Rename variable from data to d to maintain consistency between driver
functions, such as dw_pci_setup_msi_msg().

No functional change is intended.
Signed-off-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Joao Pinto <jpinto@synopsys.com>
Cc: Jingoo Han <jingoohan1@gmail.com>