doc: fix typo in driver subsection of kernel

This commit fixes a type in kernel/driver/index.rst,
present in the "Drivers that do not use Zephyr Device
Model" subsection

Signed-off-by: Dhruv Menon <dhruvmenon1104@gmail.com>

doc/kernel/drivers/index.rst

@@ -590,7 +590,7 @@ would be in the driver config struct:
 Drivers that do not use Zephyr Device Model
 ===========================================
 
-Some drivers or driver-like code may not user Zephyr's device model,
+Some drivers or driver-like code may not use Zephyr's device model,
 and alternative storage must be arranged for the MMIO data. An
 example of this are timer drivers, or interrupt controller code.