sparc64: Kill .fixup section bloat.

This is an implementation of a suggestion made by Chris Torek:
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Something else I noticed in passing: the EX and EX_LD/EX_ST macros
scattered throughout the various .S files make a fair bit of .fixup
code, all of which does the same thing.  At the cost of one symbol
in copy_in_user.S, you could just have one common two-instruction
retl-and-mov-1 fixup that they all share.
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The following is with a defconfig build:

   text	   data	    bss	    dec	    hex	filename
3972767	 344024	 584449	4901240	 4ac978	vmlinux.orig
3968887	 344024	 584449	4897360	 4aba50	vmlinux

Signed-off-by: David S. Miller <davem@davemloft.net>