clk: si5351: Delete an error message for a failed memory allocation in si5351_i2c_probe()

The script "checkpatch.pl" pointed information out like the following.

* CHECK: Comparison to NULL could be written "!drvdata"

  Thus adjust this expression.

* WARNING: Possible unnecessary 'out of memory' message

  Thus remove such a statement here.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>