max8997_charger: Fix unsigned value for less than zero
max8997_charger: Fix unsigned value for less than zero

The 'val' is a 'unsigned char', so it is never less than zero.

Signed-off-by: Jonghwan Choi <a1b1c34da4eddaa3495f0b6a971517234e873a08@gmail.com>
Acked-by: MyungJoo Ham <84146178f7c201fa3079bfc93fccba71d81dffe3@samsung.com>
Signed-off-by: Anton Vorontsov <1d765a3da7f714ffaadb979466c507aa3415181f@gmail.com>

KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas