rtl8139: use variadic macro for debug statements

rtl8139: use variadic macro for debug statements

Removes double (( )) to make DEBUG_PRINT compatible with real function calls.
Change the name to DPRINTF to be consistent with other DPRINTF macros
throughout qemu.
Include the "RTL8139: " prefix in the macro. This changes some debug output
slightly since the prefix wasn't present on all lines.

Part of the change was done using the "coccinelle" tool with the following
small semantic match:
    @@ expression E; @@

    - DEBUG_PRINT((E))
    + DPRINTF(E)

Signed-off-by: Benjamin Poirier <[email protected]>
Cc: Igor V. Kovalenko <[email protected]>
Reviewed-by: Stefan Hajnoczi <[email protected]>
Signed-off-by: Aurelien Jarno <[email protected]>