[BOLT][AARCH64] Skip R_AARCH64_LD_PREL_LO19 relocation

Supress failed to analyze relocations warning for R_AARCH64_LD_PREL_LO19
relocation. This relocation is mostly used to get value stored in CI and
we don't process it since we are caluclating target address using the
instruction value in evaluateMemOperandTarget().

Differential Revision: https://reviews.llvm.org/D127413