can: c_can_pci: fix compilation on non HAVE_CLK archs

In commit:

  5b92da04 c_can_pci: generic module for C_CAN/D_CAN on PCI

the c_can_pci driver has been added. It uses clk_*() functions
resulting in a link error on archs without clock support. This
patch removed these clk_() functions as these parts of the driver
are not tested.

Cc: Federico Vaga <federico.vaga@gmail.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>