Fixed the firmware to use a more stable clock

I have no need for the external crystal and from scope measurements I
saw that it was incredibly bad looking. I may have damaged the crystal
and I was getting intermittent behavior from the microcontroller,
especially once I started sending LED commands over SPI.

kl2-ws2811/src/main.c

@@ -25,9 +25,9 @@ int main(void)
     SIM_SOPT2 |= SIM_SOPT2_CLKOUTSEL(2);
     PORTC_PCR3 = PORT_PCR_MUX(5);*/
 
-    // Set the PLL to 96MHz (divided by 2 for the 48MHz system clock and
-    // by 2 again for the 24MHz bus clock).
-    osc_set_pll(96000000, 1, 1);
+    // Use the internal FLL. The circuit on my board for the external crystal
+    // is badly designed and I believe its unstable.
+    osc_set_fll(OSC_FLL_48MHZ, 0, 1);
 
     // Select the PLL for the USB clock source