[RISCV] Support resolving fixup_riscv_call and add to MCFixupKindInfo table

Resolving fixup_riscv_call by assembler when the linker relaxation diabled
and the function and callsite within the same compile unit.

And also adding static_assert after Infos array declaration
to avoid missing any new fixup in MCFixupKindInfo in the future.

Differential Revision: https://reviews.llvm.org/D47126

llvm-svn: 333487