NULL pointer check in sdpu_build_attrib_entry

Use case: NULL pointer check in sdpu_build_attrib_entry

Crash observed during BT stability test

Failure: Crash observed while accessing p_attr->value_ptr

Root cause: There is no null check for p_attr->value_ptr while
accessing it in sdpu_build_attrib_entry

Fix: Fixing this issue by adding null check for p_attr->value_ptr
while accessing it in sdpu_build_attrib_entry

Bug: 21896912
Change-Id: I1dd352a33ff6f86add7d1b1bfdf240d1b7992b83