media: s5p_mfc_enc: get rid of new warnings

media: s5p_mfc_enc: get rid of new warnings

The values of enc_y_addr and enc_c_addr are initialized by
s5p_mfc_hw_call(), but, in thesis, this macro might be doing
nothing, if the get_enc_frame_buffer() is not declared.
That causes those GCC warnings:

	drivers/media/platform/s5p-mfc/s5p_mfc_enc.c:1242 enc_post_frame_start() error: uninitialized symbol 'enc_y_addr'.
	drivers/media/platform/s5p-mfc/s5p_mfc_enc.c:1243 enc_post_frame_start() error: uninitialized symbol 'enc_c_addr'.
	drivers/media/platform/s5p-mfc/s5p_mfc_enc.c:1256 enc_post_frame_start() error: uninitialized symbol 'enc_y_addr'.
	drivers/media/platform/s5p-mfc/s5p_mfc_enc.c:1257 enc_post_frame_start() error: uninitialized symbol 'enc_c_addr'.

Change the logic by initializing those constants to zero,
with should hopefully do the right thing.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>