Removes unused code from the unified SVM memory fill test.
Adds an informational message when a unified SVM capability combination
is skipped for memcpy and memfill.
* Refactor check_for_common_memory_type to only check for device access.
* rename check_for_common_memory_type to caps_compatibility_check
* Update test_unified_svm_mem_cpy and test_unified_svm_mem_fill.
fixes#2517
Signed-off-by: John Kesapides <john.kesapides@arm.com>