tpm: st33zp24: remove redundant null check on chip

Currently chip is being dereferenced by the call to dev_get_drvdata
before it is being null checked, however, chip can never be null, so
this check is misleading and redundant. Remove it.

Detected by CoverityScan, CID#1357806 ("Dereference before null check")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Jarkko Sakkinen <jarkkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkkko.sakkinen@linux.intel.com>