app/channel: fixup c-style casting

Fix up c-style casting in app/channel.cpp:102

Change-Id: Ie6da0ff238856e01305127395d48ec161a30c4a1
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/app/channel.cpp b/app/channel.cpp
index 8d765c5..9db9ea8 100644
--- a/app/channel.cpp
+++ b/app/channel.cpp
@@ -99,7 +99,7 @@
                                  ipmi_context_t context)
 {
     ipmi_ret_t rc = IPMI_CC_OK;
-    uint8_t* p = (uint8_t*)request;
+    auto* p = static_cast<uint8_t*>(request);
     int channel = (*p) & CHANNEL_MASK;
     std::string ethdevice = ipmi::network::ChanneltoEthernet(channel);