arm: mediatek: remove unused binman config

The binman-option BINMAN_FDT is introduced by this commit:
commit 3c10dc95 ("binman: Add a library to access binman entries")
BINMAN_FDT being selected when BINMAN=y that resulting in mt7623
and mt7622 are unable to boot. The root cause of this issue is commit:
commit cbd2fba1 ("arm: MediaTek: add basic support for MT7629 boards")
select BINMAN=y in all mediatek SoCs, and others mediatek SoCs not
expect to use BINMAN_FDT.
This patch remove BINMAN=y option when ARCH_MEDIATEK=y and
move this to the specify SoCs part config.

Signed-off-by: Sam Shih <sam.shih@mediatek.com>
Tested-by: Frank Wunderlich <frank-w@public-files.de>