drm/tidss: fix spelling mistakes "bufer" and "requsted"

There are two spelling mistakes in warning and debug messages.
Fix them.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Jyri Sarha <jsarha@ti.com>
Tested-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Jyri Sarha <jsarha@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200224174226.387874-1-colin.king@canonical.com