Fix sparc prologue skipping

Fix sparc prologue skipping

sparc can fail at inline prologue skipping.  Andrew Burgess tracked
this down to sparc32_skip_prologue, which should use
skip_prologue_using_sal rather than its hand-rolled variant.

I don't have a good way to test this with the gdb test suite (is there
a board file for using qemu?  That would help), but it fixes a
regression in the internal AdaCore test suite.  We've had this patch
internally at AdaCore for a while, but I just now finally got around
to making sure that backing it out reintroduces the problem.

gdb/ChangeLog
2020-09-21  Tom Tromey  <tromey@adacore.com>

	* sparc-tdep.c (sparc32_skip_prologue): Use
	skip_prologue_using_sal.