meta-google: gbmc-ncsi-config: ip-from-ra: Fix regex

Our current regex for looking at the DNS search list for a valid
hostname is not quite correct if there is any extra space in the text
output due to the program outputting extra spaces for single item lists.

Tested: Hostname is parsing correctly again on a smartnic platform.

Change-Id: Ibf267b63d5399049b9746b28da124e712c33a144
Signed-off-by: William A. Kennington III <wak@google.com>