Fix incorrect values for value_regs, and incomplete values for
invalidate_regs in RegisterInfos_arm. The value_regs entry needs
to list only one base (i.e. larger) register that needs to be read
to get the value for this register, while invalidate_regs needs to list
all other registers (including pseudo-register) whose values would
change when this register is written to.
While at it, introduce helper macros for the definitions.