remoteproc: ti_k3: fix -Wcast-function-type warning

remoteproc: ti_k3: fix -Wcast-function-type warning

The function cast causes a warning with "make W=1"

drivers/remoteproc/ti_k3_r5_remoteproc.c: In function 'k3_r5_probe':
drivers/remoteproc/ti_k3_r5_remoteproc.c:1368:12: warning: cast between incompatible function types from 'int (*)(struct platform_device *)' to 'void (*)(void *)' [-Wcast-function-type]

Rewrite the code to avoid the cast, and fix the incorrect return
type of the callback.

Fixes: 6dedbd1d5443 ("remoteproc: k3-r5: Add a remoteproc driver for R5F subsystem")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20201026160533.3705998-1-arnd@kernel.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>