Remove redundant macro definitions from ia64 sfp-machine.h.

After the changes to use the copy attribute, building glibc for ia64
fails, even with older compilers, because
sysdeps/ia64/fpu/sfp-machine.h has a definition of _strong_alias that
now differs from the one in libc-symbols.h.

That definition is a relic of this file coming from libgcc, as are
some other such macro definitions in this file; in the glibc context,
there is no need for those macros, and this patch removes them to fix
the build.

Tested with build-many-glibcs.py for ia64-linux-gnu.

	* sysdeps/ia64/fpu/sfp-machine.h (__LITTLE_ENDIAN): Remove.
	(__BIG_ENDIAN): Likewise.
	(__BYTE_ORDER): Likewise.
	(strong_alias): Likewise.
	(_strong_alias): Likewise.