loongarch32 build failure on 32-bit host

gas/config/tc-loongarch.c: In function ‘assember_macro_helper’:
gas/config/tc-loongarch.c:915:28: error: right shift count >= width of type [-Werror=shift-count-overflow]
  915 |       hi32 = insn->args[1] >> 32;
      |                            ^~

One possible fix is to make offsetT a 64-bit type for loongarch32.
This also makes bfd/targmatch.h (generated from bfd/config.bfd)
consistent since the loongarch32 match is inside #ifdef BFD64.

	* config.bfd (loongarch32-*): Set want64.