camerad: zero memory before returning from MemoryManager::alloc (#30781)

* zero memory

* remove redundant memset

---------

Co-authored-by: Comma Device <device@comma.ai>
old-commit-hash: b9080d23627849aafc4969d39df50cc615ffecdf

system/camerad/cameras/camera_qcom2.cc

@@ -135,7 +135,6 @@ int CameraState::sensors_init() {
   buf_desc[1].size = buf_desc[1].length = 196;
   buf_desc[1].type = CAM_CMD_BUF_I2C;
   auto power_settings = mm.alloc<struct cam_cmd_power>(buf_desc[1].size, (uint32_t*)&buf_desc[1].mem_handle);
-  memset(power_settings.get(), 0, buf_desc[1].size);
 
   // power on
   struct cam_cmd_power *power = power_settings.get();

system/camerad/cameras/camera_util.cc

@@ -1,5 +1,7 @@
 #include "system/camerad/cameras/camera_util.h"
 
+#include <string.h>
+
 #include <cassert>
 
 #include <sys/ioctl.h>
@@ -111,6 +113,7 @@ void *MemoryManager::alloc_buf(int size, uint32_t *handle) {
     size_lookup[ptr] = size;
   }
   lock.unlock();
+  memset(ptr, 0, size);
   return ptr;
 }