drm/tiny: sharp-memory: fix pointer error dereference

[ Upstream commit 4612074 ]

The function devm_drm_dev_alloc() returns a pointer error upon failure
not NULL. Change null check to pointer error check.

Detected by Smatch:
drivers/gpu/drm/tiny/sharp-memory.c:549 sharp_memory_probe() error:
'smd' dereferencing possible ERR_PTR()

Fixes: b8f9f21 ("drm/tiny: Add driver for Sharp Memory LCD")
Signed-off-by: Ethan Tidmore <ethantidmore06@gmail.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patch.msgid.link/20260216040438.43702-1-ethantidmore06@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: Ethan Tidmore

drivers/gpu/drm/tiny/sharp-memory.c

@@ -541,8 +541,8 @@ static int sharp_memory_probe(struct spi_device *spi)
 
 	smd = devm_drm_dev_alloc(dev, &sharp_memory_drm_driver,
 				 struct sharp_memory_device, drm);
-	if (!smd)
-		return -ENOMEM;
+	if (IS_ERR(smd))
+		return PTR_ERR(smd);
 
 	spi_set_drvdata(spi, smd);