misc: Delete the now unnecessary create methods.

Most create() methods are no longer necessary. This change deletes them,
and occasionally moves some code from them into the constructors they
call.

Change-Id: Icbab29ba280144b892f9b12fac9e29a0839477e5
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/36536
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/dev/i2c/bus.cc

@@ -234,9 +234,3 @@ I2CBus::unserialize(CheckpointIn &cp)
     UNSERIALIZE_SCALAR(i2cAddr);
     UNSERIALIZE_SCALAR(message);
 }
-
-I2CBus*
-I2CBusParams::create() const
-{
-    return new I2CBus(*this);
-}