bug: fix dead code in luxminer _get_mac and _get_hashrate

Remove erroneous 'return None' statements placed outside except
blocks, making all subsequent logic unreachable. Same pattern was
already fixed for _get_wattage in 63bf0cd.

Author: wilfredallyn

pyasic/miners/backends/luxminer.py

@@ -233,13 +233,13 @@ async def _get_mac(self, rpc_config: dict | None = None) -> str | None:
                 rpc_config = await self.rpc.config()
             except APIError:
                 pass
-        return None
 
         if rpc_config is not None:
             try:
                 return rpc_config["CONFIG"][0]["MACAddr"].upper()
             except KeyError:
                 pass
+        return None
 
     async def _get_hashrate(
         self, rpc_summary: dict | None = None
@@ -249,7 +249,6 @@ async def _get_hashrate(
                 rpc_summary = await self.rpc.summary()
             except APIError:
                 pass
-        return None
 
         if rpc_summary is not None:
             try:
@@ -259,6 +258,7 @@ async def _get_hashrate(
                 ).into(self.algo.unit.default)
             except (LookupError, ValueError, TypeError):
                 pass
+        return None
 
     async def _get_hashboards(self, rpc_stats: dict | None = None) -> list[HashBoard]:
         if self.expected_hashboards is None: