Fixes to DNBArchImpl in debugserver to correctly get/set

the register state when debugging AArch32 programs (armv7
programs running on an armv8 processor).  Most notably,
there is no "fpscr" register in the register context -
there is an fpsr and an fpcr.

Also fix a bug where the floating point values could not
be written in armv7 processes.
<rdar://problem/18977767> 

llvm-svn: 226244