PCI: epf-test: Simplify read/write/copy test functions

PCI: epf-test: Simplify read/write/copy test functions

The function pci_epf_test_cmd_handler() uses the register BAR address as a
pointer to a struct pci_epf_test_reg to determine the command sent by the
host and to execute the test function accordingly. There is no need for
doing this assignment again in each of the read, write and copy test
functions. We can simply pass the reg pointer as an argument to the
functions pci_epf_test_write(), pci_epf_test_read() and
pci_epf_test_copy().

Link: https://lore.kernel.org/r/20230415023542.77601-7-dlemoal@kernel.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>