tools/nolibc: MIPS: drop manual stack pointer alignment

tools/nolibc: MIPS: drop manual stack pointer alignment

The stack pointer is already aligned by the kernel to a multiple of 16.
All modifications of the register have been removed from the entrypoint,
so the manual realignment is unnecessary.

Drop the manual alignment.

Suggested-by: Maciej W. Rozycki <macro@orcam.me.uk>
Link: https://lore.kernel.org/lkml/alpine.DEB.2.21.2502161523290.65342@angie.orcam.me.uk/
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Tested-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Link: https://lore.kernel.org/r/20250623-nolibc-mips-n32-v3-2-6ae2d89f4259@weissschuh.net