tpm/tpm_i2c_stm_st33: Remove reference to io_serirq

The serirq gpio pin is used only as interrupt. After driver initialization,
the serirq signal is always used through interrupt and never with gpio
kernel API.

The irq can then be initialized during the platform_data definition within the client->irq pin.

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>