remoteproc: stm32: Fix incorrect type in assignment for va

The sparse tool complains about the attribute conversion between
a _iomem void * and a void *:

stm32_rproc.c:122:12: sparse: sparse: incorrect type in assignment (different address spaces) @@     expected void *va @@     got void [noderef] __iomem * @@
stm32_rproc.c:122:12: sparse:     expected void *va
stm32_rproc.c:122:12: sparse:     got void [noderef] __iomem *

Add '__force' to explicitly specify that the cast is intentional.
This conversion is necessary to cast to virtual addresses pointer,used,
by the remoteproc core.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202312150052.HCiNKlqB-lkp@intel.com/


Fixes: 13140de0 ("remoteproc: stm32: add an ST stm32_rproc driver")
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Link: https://lore.kernel.org/r/20240117135312.3381936-2-arnaud.pouliquen@foss.st.com


Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>