dm: core: Fix iteration over driver_info records

We should only perform additional iteration steps when needed to
initialize the parent of a device. Other binding errors (such as a
missing driver) should not lead to additional iteration steps.

Unnecessary iteration steps can cause issues when memory is tightly
constrained (such as in the TPL/SPL) since device_bind_by_name()
unconditionally allocates memory for a struct udevice. On the SanCloud
BBE this led to boot failure caused by memory exhaustion in the SPL
when booting from SPI flash.

Signed-off-by: Paul Barker <paul.barker@sancloud.com>