spi: offload: fix use after free

spi: offload: fix use after free

Fix a use after free bug in devm_spi_offload_get() where a pointer
was dereferenced after being freed. Instead, add a new local variable
to avoid needing to use the resource pointer to access the offload
pointer.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202502112344.7ggtFzyn-lkp@intel.com/
Fixes: 5a19e1985d01 ("spi: axi-spi-engine: implement offload support")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250212-spi-offload-fixes-v1-2-e192c69e3bb3@baylibre.com
Signed-off-by: Mark Brown <broonie@kernel.org>