greybus: move is_gb_* functions out of greybus.h

The functions below are only used within the context of
drivers/greybus/core.c, so move them all into core and drop their 'inline'
specifiers:

is_gb_host_device(), is_gb_module(), is_gb_interface(), is_gb_control(),
is_gb_bundle() and is_gb_svc().

Suggested-by: Alex Elder <elder@ieee.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: "Ricardo B. Marliere" <ricardo@marliere.net>
Reviewed-by: Alex Elder <elder@linaro.org>
Link: https://lore.kernel.org/r/20240226-device_cleanup-greybus2-v1-1-5f7d1161e684@marliere.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

greybus: constify the struct device_type usage

Since commit aed65af1cc2f ("drivers: make device_type const"), the driver
core can properly handle constant struct device_type. Move the
greybus_hd_type, greybus_module_type, greybus_interface_type,
greybus_control_type, greybus_bundle_type and greybus_svc_type variables to
be constant structures as well, placing it into read-only memory which can
not be modified at runtime.

Signed-off-by: "Ricardo B. Marliere" <ricardo@marliere.net>
Reviewed-by: Alex Elder <elder@linaro.org>
Link: https://lore.kernel.org/r/20240219-device_cleanup-greybus-v1-1-babb3f65e8cc@marliere.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

greybus: make greybus_bus_type const

Now that the driver core can properly handle constant struct bus_type,
move the greybus_bus_type variable to be a constant structure as well,
placing it into read-only memory which can not be modified at runtime.

Cc: Alex Elder <elder@kernel.org>
Cc: greybus-dev@lists.linaro.org
Reviewed-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/2024010517-handgun-scoreless-05e7@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

staging: greybus: move core include files to include/linux/greybus/

With the goal of moving the core of the greybus code out of staging, the
include files need to be moved to include/linux/greybus.h and
include/linux/greybus/

Cc: Vaibhav Hiremath <hvaibhav.linux@gmail.com>
Cc: Johan Hovold <johan@kernel.org>
Cc: Vaibhav Agarwal <vaibhav.sr@gmail.com>
Cc: Rui Miguel Silva <rmfrfs@gmail.com>
Cc: David Lin <dtwlin@gmail.com>
Cc: "Bryan O'Donoghue" <pure.logic@nexus-software.ie>
Cc: greybus-dev@lists.linaro.org
Cc: devel@driverdev.osuosl.org
Acked-by: Mark Greer <mgreer@animalcreek.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Alex Elder <elder@kernel.org>
Link: https://lore.kernel.org/r/20190825055429.18547-8-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>