drm/v3d/v3d_drv: 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.
Also, we can create a variable for the mask to solve the
alignment issue.

Fixes: 334dd38a ("drm/v3d: Set dma_mask as well as coherent_dma_mask")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220110013807.4105270-1-jiasheng@iscas.ac.cn