Move the s5p-mfc firmware out of its subdirectory

The driver does not include this subdirectory name when requesting
firmware.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Arun Kumar K <arun.kk@samsung.com>
Cc: linux-samsung-soc <linux-samsung-soc@vger.kernel.org>
Cc: Tomasz Figa <t.figa@samsung.com>

WHENCE

@@ -2250,11 +2250,11 @@ Licence: Redistributable. See LICENCE.atheros_firmware for details
 
 Driver: s5p-mfc - Samsung MFC video encoder/decoder driver
 
-File: s5p-mfc/s5p-mfc.fw
+File: s5p-mfc.fw
-File: s5p-mfc/s5p-mfc-v6.fw
+File: s5p-mfc-v6.fw
-File: s5p-mfc/s5p-mfc-v6-v2.fw
+File: s5p-mfc-v6-v2.fw
-File: s5p-mfc/s5p-mfc-v7.fw
+File: s5p-mfc-v7.fw
-File: s5p-mfc/s5p-mfc-v8.fw
+File: s5p-mfc-v8.fw
 
 Licence:
 Samsung grants permission to use and redistribute aforementioned firmware