chromeec: fix an uninitialized local variable

google_chromeec_command() may only write the 1 or 2 bytes to
variable r (4 bytes). However, this api returns 4 bytes data.
To avaid returning the incorrect data, we need to initialize the
local variable.

BUG=b:76442548
BRANCH=none
TEST=write 2 bytes data into the flash, then, read by cbi_get_uint32

Change-Id: I3395c97ab6bfd7882d7728310de8a29041190e76
Signed-off-by: Zhuohao Lee <zhuohao@chromium.org>
Reviewed-on: https://review.coreboot.org/25460
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/ec/google/chromeec/ec.c

@@ -563,7 +563,7 @@ static int cbi_get_uint32(uint32_t *id, uint32_t type)
 {
 	struct chromeec_command cmd;
 	struct ec_params_get_cbi p;
-	uint32_t r;
+	uint32_t r = 0;
 	int rv;
 
 	p.type = type;