memory: renesas-rpc-if: Move resource acquisition to .probe()

While the acquired resources are tied to the lifetime of the RPC-IF core
device (through the use of managed resource functions), the actual
resource acquisition is triggered from the HyperBus and SPI child
drivers.  Due to this mismatch, unbinding and rebinding the child
drivers manually fails with -EBUSY:

    # echo rpc-if-hyperflash > /sys/bus/platform/drivers/rpc-if-hyperflash/unbind
    # echo rpc-if-hyperflash > /sys/bus/platform/drivers/rpc-if-hyperflash/bind
    rpc-if ee200000.spi: can't request region for resource [mem 0xee200000-0xee2001ff]
    rpc-if-hyperflash: probe of rpc-if-hyperflash failed with error -16

The same is true for rpc-if-spi.

Fix this by moving all resource acquisition to the core driver's probe
routine.

Fixes: ca7d8b98 ("memory: add Renesas RPC-IF driver")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/c1012ef1de799e08a70817ab7313794e2d8d7bfb.1669213027.git.geert+renesas@glider.be


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>