ALSA: docs: fix typo

GFP_KRENEL -> GFP_KERNEL

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>

Link: https://lore.kernel.org/r/1596224129-7699-1-git-send-email-Julia.Lawall@inria.fr
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Documentation/sound/kernel-api/writing-an-alsa-driver.rst

@@ -3579,7 +3579,7 @@ dependent on the bus. For normal devices, pass the device pointer
 ``SNDRV_DMA_TYPE_DEV`` type. For the continuous buffer unrelated to the
 bus can be pre-allocated with ``SNDRV_DMA_TYPE_CONTINUOUS`` type.
 You can pass NULL to the device pointer in that case, which is the
-default mode implying to allocate with ``GFP_KRENEL`` flag.
+default mode implying to allocate with ``GFP_KERNEL`` flag.
 If you need a different GFP flag, you can pass it by encoding the flag
 into the device pointer via a special macro
 :c:func:`snd_dma_continuous_data()`.