intel/bd82x6x: Fix a small mistake in DIR_ROUTE

The register is 16-bits wide. If the DIR_ROUTE call ordering was
reversed the previous writes would get overwritten.

See page 407ff on the Intel C216 datasheet, which says
"Size: 16bits" with "Default: 3210h" for all DnnIR registers.

This also makes sense given the register offsets:
3140h–3141h D31IR Device 31 Interrupt Route 3210h R/W
[3142h would be D30IR]
3144h–3145h D29IR Device 29 Interrupt Route 3210h R/W
3146h–3147h D28IR Device 28 Interrupt Route 3210h R/W
3148h–3149h D27IR Device 27 Interrupt Route 3210h R/W
314Ch–314Dh D26IR Device 26 Interrupt Route 3210h R/W
3150h–3151h D25IR Device 25 Interrupt Route 3210h R/W
[discontinuity in register addresses here]
315Ch–315Dh D22IR Device 22 Interrupt Route 3210h R/W
[315Eh would be D21IR]
3160h–3161h D20IR Device 20 Interrupt Route 3210h R/W

Change-Id: I970abbacbc2c59e86c1726171272b8779758e53e
Signed-off-by: Tobias Diedrich <ranma+coreboot@tdiedrich.de>
Reviewed-on: https://review.coreboot.org/22621
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>

src/southbridge/intel/bd82x6x/pch.h

@@ -418,7 +418,7 @@ int rtc_failure(void);
 #define SOFT_RESET_DATA 0x38f8
 
 #define DIR_ROUTE(x,a,b,c,d) \
-  RCBA32(x) = (((d) << DIR_IDR) | ((c) << DIR_ICR) | \
+  RCBA16(x) = (((d) << DIR_IDR) | ((c) << DIR_ICR) | \
                ((b) << DIR_IBR) | ((a) << DIR_IAR))
 
 #define RC		0x3400	/* 32bit */