Thumb 22 bit pc-relative branch. The lowest bit must be zero and is
not stored in the instruction. The 2nd lowest bit comes from a 1 bit
field in the instruction.
+ENUM
+ BFD_RELOC_ARM_PCREL_CALL
+ENUMDOC
+ ARM 26-bit pc-relative branch for an unconditional BL or BLX instruction.
+ENUM
+ BFD_RELOC_ARM_PCREL_JUMP
+ENUMDOC
+ ARM 26-bit pc-relative branch for B or conditional BL instruction.
ENUM
BFD_RELOC_THUMB_PCREL_BRANCH7