binman: Add option for pointing to separate description

binman: Add option for pointing to separate description

Adding binman node with target images description can be unwanted feature
but as of today there is no way to disable it.
Also on size constrained systems it is not useful to add binman description
to DTB.
Introduce BINMAN_DTB Kconfig symbol which allows separate DTB for target
from DTB for binman itself.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/f1379d2587f9bf279a7a75c318aabbc1b35ee0c6.1730452668.git.michal.simek@amd.com