usb: musb: gadget: remove redundant condition

This patch removes redundant condition.

 (!A || (A && B)) is the same as (!A || B).

Fixes indentation too.

Tested by: compilation only
Caught by: cppcheck

Signed-off-by: Geyslan G. Bem <geyslan@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>