drivers: sensor: Check i2c device pointer is non-null in bq274xx

Fixes the bq274xx sensor driver to check the i2c device pointer is
non-null, rather than the bq274xx sensor device pointer. This appears to
be the originally intended check based on the LOG_ERR message.

Coverity CID: 210035

Signed-off-by: Maureen Helm <maureen.helm@nxp.com>