tpm_tis: Do *not* flush uninitialized work

tpm_tis_core_init() may fail before tpm_tis_probe_irq_single() is
called, in which case tpm_tis_remove() unconditionally calling
flush_work() is triggering a warning for .func still being NULL.

Cc: [e-mail] # v6.5+
Fixes: 481c2d14627d ("tpm,tpm_tis: Disable interrupts after 1000 unhandled IRQs")
Signed-off-by: Jan Beulich <[e-mail]>
Reviewed-by: Jarkko Sakkinen <[e-mail]>
Signed-off-by: Jarkko Sakkinen <[e-mail]>

drivers/char/tpm/tpm_tis_core.c

···
 		interrupt = 0;
 
 	tpm_tis_write32(priv, reg, ~TPM_GLOBAL_INT_ENABLE & interrupt);
-	flush_work(&priv->free_irq_work);
+	if (priv->free_irq_work.func)
+		flush_work(&priv->free_irq_work);
 
 	tpm_tis_clkrun_enable(chip, false);