Bluetooth: Use switch statement for Intel hardware variants

Multiple new hardware variants are planned and the simple if statement
would get really complicated and unreadable. So instead replace it with
a simple switch statement.

The change is applied to both USB and UART.

Based-on-patch-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Tedd Ho-Jeong An <tedd.an@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>