[RISCV][MC] Find matching pcrel_hi fixup in more cases.

If a symbol points to the end of a fragment, instead of searching for
fixups in that fragment, search in the next fragment.

Fixes spurious assembler error with subtarget change next to "la"
pseudo-instruction, or expanded equivalent.

Alternate proposal to fix the problem discussed in
https://reviews.llvm.org/D58759.

Testcase by Ana Pazos.

Differential Revision: https://reviews.llvm.org/D58943



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@355946 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed