If the target says that an extending load is not legal, regardless of whether

If the target says that an extending load is not legal, regardless of whether
it involves specific floating-point types, legalize should expand an
extending load to a non-extending load followed by a separate extend operation.
For example, we currently expand SEXTLOAD to EXTLOAD+SIGN_EXTEND_INREG (and
assert that EXTLOAD should always be supported).  Now we can expand that to
LOAD+SIGN_EXTEND.  This is needed to allow vector SIGN_EXTEND and ZERO_EXTEND
to be used for NEON.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111586 91177308-0d34-0410-b5e6-96231b3b80d8