drm/sti: remove redundant sign extensions

arg is long int, so arg = (arg << 22) >> 22 makes the upper 22 bits of
arg equal to bit 9 (or bit 41). But we then mask away all but bits 0-9, so
this is entirely redundant.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Vincent Abriou <vincent.abriou@st.com>

drivers/gpu/drm/sti/sti_awg_utils.c

@@ -65,7 +65,6 @@ static int awg_generate_instr(enum opcode opcode,
 
 			mux = 0;
 			data_enable = 0;
-			arg = (arg << 22) >> 22;
 			arg &= (0x3ff);
 			break;
 		case REPEAT:
@@ -77,14 +76,12 @@ static int awg_generate_instr(enum opcode opcode,
 
 			mux = 0;
 			data_enable = 0;
-			arg = (arg << 22) >> 22;
 			arg &= (0x3ff);
 			break;
 		case JUMP:
 			mux = 0;
 			data_enable = 0;
 			arg |= 0x40; /* for jump instruction 7th bit is 1 */
-			arg = (arg << 22) >> 22;
 			arg &= 0x3ff;
 			break;
 		case STOP:
@@ -94,7 +91,6 @@ static int awg_generate_instr(enum opcode opcode,
 		case RPTSET:
 		case RPLSET:
 		case HOLD:
-			arg = (arg << 24) >> 24;
 			arg &= (0x0ff);
 			break;
 		default: