Remove no-op function pointer null checks, NFC

Null-checking functions which aren't marked weak_import is a no-op
(the compiler rewrites the check to 'true'), regardless of whether a
library providing its definition is weak-linked. If the deployment
target is greater than the minimum requirement, the availability markup
on APIs does not lower to weak_import.

Remove no-op null checks to clean up the code and silence warnings.

Differential Revision: https://reviews.llvm.org/D40812

llvm-svn: 319936
diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp
index c3f0d5d..949cf19 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp
@@ -600,10 +600,9 @@
 #if defined(HAVE_LIBCOMPRESSION)
   // libcompression is weak linked so check that compression_decode_buffer() is
   // available
-  if (compression_decode_buffer != NULL &&
-      (m_compression_type == CompressionType::ZlibDeflate ||
-       m_compression_type == CompressionType::LZFSE ||
-       m_compression_type == CompressionType::LZ4)) {
+  if (m_compression_type == CompressionType::ZlibDeflate ||
+      m_compression_type == CompressionType::LZFSE ||
+      m_compression_type == CompressionType::LZ4) {
     compression_algorithm compression_type;
     if (m_compression_type == CompressionType::LZFSE)
       compression_type = COMPRESSION_LZFSE;