CONFIG_BOOTDELAY default should not affect runtime

Because the code that handles bootdelay is compiled in conditionally
based on the default value, you are restricted in the default,
regardless of what you want the runtime options to be.

Change the source to always check if any default is given so that other
values can be selected and used at runtime.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>