i2c: core: Check for error pointer for fwnode

i2c: core: Check for error pointer for fwnode

Theoretically it's possible that fwnode is returned by some API,
that may return an error pointer (and we have, for example,
fwnode_find_reference() which does that). If such an fwnode
is supplied to the i2c core APIs the functions will perform
unneeded loops and checks. Avoid this by preventively checking
for an error pointer and bail out immediately.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>