clk: imx6q: fix typo in CAN clock definition

commit ee360274 ("clk: imx: Add clock support for imx6qp")
introduced a regression due to a subtle typo in the 'can_root' clock
definition. The effect is that trying to configure the bitrate of the
can interfaces fails with -EDOM or produces a division by zero error
due to the clock_freq of the can serial clock being reported as '0'.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Fixes: ee360274 ("clk: imx: Add clock support for imx6qp")
Signed-off-by: Shawn Guo <shawnguo@kernel.org>