tpm_tis: Revert "tpm_tis: Disable interrupts on ThinkPad T490s"

Since for MMIO driver using FIFO registers, also known as tpm_tis, the
default (and tbh recommended) behaviour is now the polling mode, the
"tristate" workaround is no longer for benefit.

If someone wants to explicitly enable IRQs for a TPM chip that should be
without question allowed. It could very well be a piece hardware in the
existing deny list because of e.g. firmware update or something similar.

While at it, document the module parameter, as this was not done in 2006
when it first appeared in the mainline.

Link: https://lore.kernel.org/linux-integrity/20201015214430.17937-1-jsnitsel@redhat.com/
Link: https://lore.kernel.org/all/1145393776.4829.19.camel@localhost.localdomain/
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

Documentation/admin-guide/kernel-parameters.txt

@@ -6340,6 +6340,13 @@
 			This will guarantee that all the other pcrs
 			are saved.
 
+	tpm_tis.interrupts= [HW,TPM]
+			Enable interrupts for the MMIO based physical layer
+			for the FIFO interface. By default it is set to false
+			(0). For more information about TPM hardware interfaces
+			defined by Trusted Computing Group (TCG) see
+			https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
+
 	tp_printk	[FTRACE]
 			Have the tracepoints sent to printk as well as the
 			tracing ring buffer. This is useful for early boot up