hwmon: (ads7871) Replace sprintf() with sysfs_emit()

hwmon: (ads7871) Replace sprintf() with sysfs_emit()

Use sysfs_emit() instead of sprintf() in the sysfs show function
voltage_show() to comply with the preferred kernel interface for
writing to sysfs buffers, which ensures PAGE_SIZE buffer limits
are respected.

No functional change intended.

Note: Not runtime tested due to lack of hardware.

Signed-off-by: Tabrez Ahmed <tabreztalks@gmail.com>
Link: https://lore.kernel.org/r/20260307083815.12095-1-tabreztalks@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>