tpm: infineon section mismatch

Fix section mismatch by making the driver template variable name
match one of the whitelisted variable names in modpost.

WARNING: vmlinux.o(.data+0x7a9e8): Section mismatch: reference to .init.text:tpm_inf_pnp_probe (between 'tpm_inf_pnp' and 'cn_idx')

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Marcel Selhorst <tpm@selhorst.net>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>