Optimize lcd-ssd1303 driver (clip series)

Saves 100+ bytes (50 of it in iram), saves a bit of power

Internal LCD clock decreased but with added efficiency of drawing routines
loses only around 2 Hz on the scanrate (~75Hz) while fps is slightly increased

Column offsets are now calculated outside the loops saving a few instructions

Passing a LCD_NOP command after lcd_update turns off Data/Cmd# gpio
saving a bit more power

Added a function lcd_write_cmd_triple() that allows 3 commands to be sent at once
when enabled with LCD_USE_FIFO_FOR_COMMANDS it sends them back to back without
checking FIFO status in between or sending to thhe D/C# Gpio.
Makes an assumption about the FIFO being large enough to
accept 3 commands after being emptied which should be the case on the
clipv1, clipv2, clipplus. I have only enabled it for the clip plus
as thats the only device I have to test it on.

On clip+ the SSP clock is now turned off when screen is off

Change-Id: Ib5fd24697bfe4ac8b8ee017361e789e4a7910d21

firmware/target/arm/as3525/sansa-clip/lcd-clip.c

@@ -69,6 +69,34 @@ void lcd_write_command(int byte)
         ;
 }
 
+void lcd_write_cmd_triplet(int cmd1, int cmd2, int cmd3)
+{
+#ifndef LCD_USE_FIFO_FOR_COMMANDS
+    lcd_write_command(cmd1);
+    lcd_write_command(cmd2);
+    lcd_write_command(cmd3);
+#else
+    /* combine writes to data register */
+
+    while ((DBOP_STAT & (1<<10)) == 0) /* While push fifo is not empty */
+        ;
+    /* FIFO is empty at this point */
+
+    /* unset D/C# (data or command) */
+    GPIOA_PIN(5) = 0;
+
+    /* Write command */
+    /* !!makes assumption FIFO is at least (3) levels deep! */
+    /* Only bits 15:12 and 3:0 of DBOP_DOUT are meaningful */
+    DBOP_DOUT = (cmd1 << 8) | cmd1;
+    DBOP_DOUT = (cmd2 << 8) | cmd2;
+    DBOP_DOUT = (cmd3 << 8) | cmd3;
+    /* While push fifo is not empty */
+    while ((DBOP_STAT & (1<<10)) == 0)
+        ;
+#endif
+}
+
 void lcd_write_data(const fb_data* p_bytes, int count)
 {
     volatile int i = 0;