sparc64: Fix prototype warning for uprobe_trap

Fix the following warning:
arch/sparc/kernel/uprobes.c:237:17: warning: no previous prototype for ‘uprobe_trap’

Add a prototype to kernel/kernel.h to silence the warning.
This is a fix already used for other trap handlers.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: David S. Miller <davem@davemloft.net>
Reviewed-by: Andreas Larsson <andreas@gaisler.com>
Tested-by: Andreas Larsson <andreas@gaisler.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20240330-sparc64-warnings-v1-5-37201023ee2f@ravnborg.org
Signed-off-by: Andreas Larsson <andreas@gaisler.com>