update ast2400 reset

add reset for ast2400

update wdt for ast2500/ast2600

[update] examin strap to know if SDRAM has
been initialized.

1. for ast2600, check if SCU100[6]==1 (SDRAM has been initialized) or
not.
2. refactor format

re-arrange modify

update

update ast2500 reset driver

update ast2500 reset driver

update ast2600 reset driver

update reset

update reset driver

remove ast_get_scu function

update for reset and clk

add ast2600 reset

update ast2500 reset

mv reset-ast2500 to aspeed folder