[Hexagon] Only handle simple types memory accesses (#120654)
The code was asserting because allowsMemoryAccess() was called with
Extended Value Type INVALID_SIMPLE_VALUE_TYPE in
HexagonISelLowering.cpp.
Fixes https://github.com/llvm/llvm-project/issues/118881
(cherry picked from commit 8177bf5022c6dfc48d236082fa02076feedd60df)