drm/panfrost: Check for error num after setting mask

Because of the possible failure of the dma_supported(), the
dma_set_mask_and_coherent() may return error num.
Therefore, it should be better to check it and return the error if
fails.

Fixes: f3ba9122 ("drm/panfrost: Add initial panfrost driver")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
[Steve: fix Fixes: line]
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220106030326.2620942-1-jiasheng@iscas.ac.cn