libopcodes/ppc: add support for disassembler styling

libopcodes/ppc: add support for disassembler styling

This commit adds disassembler styling to the libopcodes ppc
disassembler.  This conversion was pretty straight forward, I just
converted the fprintf_func calls to fprintf_styled_func calls and
added an appropriate style.

For testing the new styling I just assembled then disassembled the
source files in gas/testsuite/gas/ppc and manually checked that the
styling looked reasonable.

I think the only slightly weird case was how things like '4*cr1+eq'
are styled.  As best I can tell, this construct, used for example in
this instruction:

  crand   4*cr1+lt,4*cr1+gt,4*cr1+eq

is used to access a field of a control register.  I initially tried
styling this whole construct as a register[1], but during review it
was suggested that instead different parts of the text should have
different styles.  In this commit I propose styling '4*cr1+lt' like
this:

  4    - immediate,
  *    - text,
  cr1  - register
  +    - text
  lt   - sub-mnemonic

If the user does not request styled output from objdump, then there
should be no change in the disassembler output after this commit.

[1] https://sourceware.org/pipermail/binutils/2022-July/121771.html