tpm/tpm_i2c_stm_st33: Fix few coding style error reported by scripts/checkpatch.pl

Fix:
- WARNING: Missing a blank line after declarations
- WARNING: braces {} are not necessary for any arm of this statement

Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Peter Huewe <peterhuewe@gmx.de>