soc/intel/common: fix gsmi handler

The gsmi_exec() expects the parameter to be a pointer
to the 32-bit register storage of the SMI save state.
The previous code was passing a pointer with the value
obtained from the saved-state -- not a pointer to the
storage of the register value. This bug causes gsmi
to not log events because it's interrogating the
parameter buffer itself as if it were a pointer.

BUG=chrome-os-partner:55932

Change-Id: I37981424f1414edad1456b31cad1b99020d57db6
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/16087
Tested-by: build bot (Jenkins)
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/soc/intel/common/smihandler.c

@@ -221,7 +221,7 @@ static void southbridge_smi_gsmi(const struct
 	reg_ebx = save_state_ops->get_reg(io_smi, RBX);
 
 	/* drivers/elog/gsmi.c */
-	ret = gsmi_exec(sub_command, (u32 *)(uintptr_t)reg_ebx);
+	ret = gsmi_exec(sub_command, &reg_ebx);
 	save_state_ops->set_reg(io_smi, RAX, ret);
 }