tpm/tpm_infineon: Use struct dev_pm_ops for power management

Make the tpm_infineon driver define its PM callbacks through
a struct dev_pm_ops object rather than by using legacy PM hooks
in struct pnp_driver.

This allows the driver to use tpm_pm_suspend() as its suspend
callback directly, so we can remove the duplicated savestate code.

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>