firewire: core: determine transaction speed after detecting quirks

firewire: core: determine transaction speed after detecting quirks

Current implementation determines the maximum transaction speed supported
by the target device after reading bus information block of configuration
ROM. The read operations for root directory block are then performed at
the determined speed. However, some devices have quirks that cause issues
when transactions are performed at the determined speed.

In the first place, all devices are required to support the lowest speed
(S100) and must respond successfully to any read request within the
configuration ROM space. Therefore it is safe to postpone speed
determination until the entire configuration ROM has been read.

This commit moves the speed determination after reading root directory.

Link: https://lore.kernel.org/r/20251018035532.287124-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>