soc/intel/broadwell: Init var before use, only use when needed

root_port_init_config() pcie.c wasn't initializing a variable before
passing its pointer to pch_iobp_exec(). pch_iobp_exec() wrote the
uninitialized value into a register.
In theory, the register would only be used if data was being written,
and pch_iobp_exec()  was being used to read the data, not write it, so
this change shouldn't have any practical effect.

Fixes coverity error:
CID 1293134 (#1 of 1): Uninitialized scalar variable (UNINIT)

Change-Id: I5d17863d904c6b1ceb30d72b94cd7a40c8fbb437
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/12778
Tested-by: build bot (Jenkins)
Reviewed-by: Duncan Laurie <dlaurie@google.com>

src/soc/intel/broadwell/iobp.c

@@ -136,6 +136,7 @@ void pch_iobp_exec(u32 addr, u16 op_code, u8 route_id, u32 *data, u8 *resp)
 	/* RCBA233A[15:8] = 0xf0 RCBA233A[7:0] = Route ID */
 	RCBA16(IOBPU) = IOBPU_MAGIC | route_id;
 
+	if (op_code == IOBP_PCICFG_WRITE)
 		RCBA32(IOBPD) = *data;
 	/* Set RCBA2338[0] to trigger IOBP transaction*/
 	RCBA16(IOBPS) = RCBA16(IOBPS) | 0x1;

src/soc/intel/broadwell/pcie.c

@@ -120,7 +120,7 @@ static void pcie_iosf_port_grant_count(device_t dev)
 static void root_port_init_config(device_t dev)
 {
 	int rp;
-	u32 data;
+	u32 data = 0;
 	u8 resp, id;
 
 	if (root_port_is_first(dev)) {