exec/cpu-common: Move MUSB specific typedefs to 'hw/usb/hcd-musb.h'

exec/cpu-common: Move MUSB specific typedefs to 'hw/usb/hcd-musb.h'

The CPUReadMemoryFunc/CPUWriteMemoryFunc typedefs are legacy
remnant from before the conversion to MemoryRegions.
Since they are now only used in tusb6010.c and hcd-musb.c,
move them to "hw/usb/musb.h" and rename them appropriately.

Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200601141536.15192-4-f4bug@amsat.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>