regmap: debugfs: Fix a erroneous check after snprintf()

[ Upstream commit d3601857e14de6369f00ae19564f1d817d175d19 ]

This error handling looks really strange.
Check if the string has been truncated instead.

Fixes: f0c2319f ("regmap: Expose the driver name in debugfs")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/8595de2462c490561f70020a6d11f4d6b652b468.1693857825.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>