[SROA] Fix PR24463, a crash I introduced in SROA by allowing it to

[SROA] Fix PR24463, a crash I introduced in SROA by allowing it to
handle more allocas with loads past the end of the alloca.

I suspect there are some related crashers with slightly different
patterns, but I'll fix those and add test cases as I find them.

Thanks to David Majnemer for the excellent test case reduction here.
Made this super simple to debug and fix.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246289 91177308-0d34-0410-b5e6-96231b3b80d8