hw/sd: Remove unused legacy functions, stop killing mammoths

hw/sd: Remove unused legacy functions, stop killing mammoths

The sdcard_legacy.h header defines function prototypes for the "legacy"
SD card API, which was used by non-qdevified SD controller models.
We've now converted the only remaining non-qdev SD controller, so
we can drop the legacy API.

Entirely unused functions:
  sd_init(), sd_set_cb(), sd_enable()

Functions which now become static inside sd.c (they are the
underlying implementations of methods on SDCardClass):
  sd_do_command(), sd_write_byte(), sd_read_byte()

Removal of sd_init() means that we can also remove the
me_no_qdev_me_kill_mammoth_with_rocks flag, the codepaths that were
only reachable when it was set, and the inserted_cb and readonly_cb
qemu_irq lines that went with that.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20250128104519.3981448-11-peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>