dts: arm: st: re-enable master can gating clock for can2

Commit 57723cf4 ("dts: arm: st: Refactor DTSI files to use macro"),
which replaced raw hex codes by using STM32_CLOCK macro, causes
regression in the case of the CAN device where the previous raw value
contained more than one bit set to 1. The macro is in fact correct only
for values with a single bit set. In all other cases, raw values must
continue to be used.

Tested on STM32F429I-DISC1 board

Fixes: 57723cf4
Co-authored-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>