driver core: Remove unused platform_notify, platform_notify_remove

driver core: Remove unused platform_notify, platform_notify_remove

The "platform_notify" and "platform_notify_remove" hooks have been unused
since 00ba9357d189 ("ARM: ixp4xx: Drop custom DMA coherency and bouncing").

Remove "platform_notify" and "platform_notify_remove".  No functional
change intended.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20240325221409.1457036-1-helgaas@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>