linux-yocto: link kgdboc after the driver for UART

On MinnowBoard, when kgdboc and pch_uart are statically compiled,
kgdboc executes prior to pch_uart getting registerd. As a result,
kgdboc is unable to find serial console and kgdb mode is not
entered during boot. Changed the order of linking so that
pch_uart initialization takes place before kgdboc module is run.

JIRA: http://jira.alm.mentorg.com:8080/browse/SB-3632

Signed-off-by: Yasir-Khan <yasir_khan@mentor.com>