Fix IO direction for host Serial-TL port

[ethanwu10]

cloneType is a Chisel-internal method; use chiselTypeOf to construct an IO of the same type and direction.

cloneType appears to strip the Flipped modifier from types, so attempting to instantiate a bringup host config with a serial-TL clock driven by the DUT results in a connection failure during elaboration since both the ChipTop IO and the DigitalTop port are drivers.

Related PRs / Issues:

Type of change:

• Bug fix
• New feature
• Other enhancement

Impact:

• RTL change
• Software change (RISC-V software)
• Build system change
• Other

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