[SPARC]: Fix weak aliases

sparc_ksyms.c used to declare weak alias to several gcc intrinsics.  It
doesn't work with gcc4 anymore - it wants a declaration for the thing
we are aliasing to and that's not going to happen for something like
.mul, etc.  Replaced with direct injection of weak alias on the assembler
level - .weak <alias> followed by <alias> = <aliased>; that works on all
gcc versions.

Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>