hwrng: omap - Delete an error message in of_get_omap_rng_device_details()

The function “platform_get_irq” can log an error already.
Thus omit a redundant message for the exception handling in the
calling function.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>