Fix two spelling errors

Suggested by James Zern.

Change-Id: I5ad239c11019772078ff91b41c79764a3863c4d1

av1/encoder/encoder.h

diff --git a/av1/encoder/encoder.h b/av1/encoder/encoder.h
index 3b33e60..b8a0684 100644
--- a/av1/encoder/encoder.h
+++ b/av1/encoder/encoder.h
@@ -2441,7 +2441,7 @@
    */
   unsigned int buffer_time_index[REF_FRAMES];
   /*!
-   * Saptial layer id of the last frame that refreshed the buffer slot.
+   * Spatial layer id of the last frame that refreshed the buffer slot.
    */
   unsigned char buffer_spatial_layer[REF_FRAMES];
   /*!

av1/encoder/ratectrl.c

diff --git a/av1/encoder/ratectrl.c b/av1/encoder/ratectrl.c
index eb970f6..0c1e81c 100644
--- a/av1/encoder/ratectrl.c
+++ b/av1/encoder/ratectrl.c
@@ -564,7 +564,7 @@
   if (!cpi->ppi->use_svc && cm->prev_frame &&
       (width * height > 1.5 * cm->prev_frame->width * cm->prev_frame->height))
     q = (q + active_worst_quality) >> 1;
-  // For singler layer RPS: Bias Q based on distance of closest reference.
+  // For single layer RPS: Bias Q based on distance of closest reference.
   if (cpi->ppi->rtc_ref.bias_recovery_frame) {
     const int min_dist = av1_svc_get_min_ref_dist(cpi);
     q = q - AOMMIN(min_dist, 20);