[opengl] Modernize codebase by replacing NULL with nullptr

Fixes -Wzero-as-null-pointer-constant warning.

Test: m
Bug: 68236239
Change-Id: Ia2f91707b277954d5105f6fdb489caad9ef8848c
diff --git a/opengl/libs/EGL/FileBlobCache.cpp b/opengl/libs/EGL/FileBlobCache.cpp
index 7923715..cc42ac7 100644
--- a/opengl/libs/EGL/FileBlobCache.cpp
+++ b/opengl/libs/EGL/FileBlobCache.cpp
@@ -77,7 +77,7 @@
             return;
         }
 
-        uint8_t* buf = reinterpret_cast<uint8_t*>(mmap(NULL, fileSize,
+        uint8_t* buf = reinterpret_cast<uint8_t*>(mmap(nullptr, fileSize,
                 PROT_READ, MAP_PRIVATE, fd, 0));
         if (buf == MAP_FAILED) {
             ALOGE("error mmaping cache file: %s (%d)", strerror(errno),