hexagon: vm_events: remove unused dummy_handler()

Clang warns:

  arch/hexagon/kernel/vm_events.c:76:6: warning: no previous prototype for function 'dummy_handler' [-Wmissing-prototypes]
     76 | void dummy_handler(struct pt_regs *regs)
        |      ^
  arch/hexagon/kernel/vm_events.c:76:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
     76 | void dummy_handler(struct pt_regs *regs)
        | ^
        | static

This function appears to be entirely unused, so remove it.

Link: https://lkml.kernel.org/r/20231130-hexagon-missing-prototypes-v1-16-5c34714afe9e@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Brian Cain <bcain@quicinc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>