arm_adi_v5: fix scan-build warning [2/3]

arm_adi_v5: fix scan-build warning [2/3]

Commit d01b3d69ec17 ("arm_adi_v5: separate ROM table parsing from
command output [3/3]") introduces a new scan-build warning because
removing one return in case of error causes using uninitialized
values.

Add back the return on error.

Change-Id: I10ddc548b756d34aaccc0511f091b4caa5ec271a
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Fixes: d01b3d69ec17 ("arm_adi_v5: separate ROM table parsing from command output [3/3]")
Reviewed-on: https://review.openocd.org/c/openocd/+/7011
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>