[COFF, ARM64] Handle ADRP immediate offsets in relocations

Also handle overflow correctly in LDR/STR relocations. Even if the
offset range of a 8 byte LDR instruction is 15 bit (even if the immediate
itself is 12 bit) due to a 3 bit shift, only include up to 12 bits of offset
after doing the relocation, by limiting the range of the immediate by the
number of shifted bits.

Differential Revision: https://reviews.llvm.org/D35792

llvm-svn: 309175