fbdev: c2p: Fix link failure on non-inlining

When the compiler decides not to inline the Chunky-to-Planar core
functions, the build fails with:

c2p_planar.c:(.text+0xd6): undefined reference to `c2p_unsupported'
c2p_planar.c:(.text+0x1dc): undefined reference to `c2p_unsupported'
c2p_iplan2.c:(.text+0xc4): undefined reference to `c2p_unsupported'
c2p_iplan2.c:(.text+0x150): undefined reference to `c2p_unsupported'

Fix this by marking the functions __always_inline.

While this could be triggered before by manually enabling both
CONFIG_OPTIMIZE_INLINING and CONFIG_CC_OPTIMIZE_FOR_SIZE, it was exposed
in the m68k defconfig by commit ac7c3e4ff401b304 ("compiler: enable
CONFIG_OPTIMIZE_INLINING forcibly").

Fixes: 9012d011660ea5cf ("compiler: allow all arches to enable CONFIG_OPTIMIZE_INLINING")
Reported-by: [e-mail]
Signed-off-by: Geert Uytterhoeven <[e-mail]>
Reviewed-by: Masahiro Yamada <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/video/fbdev/c2p_core.h

···
 
 extern void c2p_unsupported(void);
 
-static inline u32 get_mask(unsigned int n)
+static __always_inline u32 get_mask(unsigned int n)
 {
 	switch (n) {
 	case 1:
···
      *  Transpose operations on 8 32-bit words
      */
 
-static inline void transp8(u32 d[], unsigned int n, unsigned int m)
+static __always_inline void transp8(u32 d[], unsigned int n, unsigned int m)
 {
 	u32 mask = get_mask(n);
 
···
      *  Transpose operations on 4 32-bit words
      */
 
-static inline void transp4(u32 d[], unsigned int n, unsigned int m)
+static __always_inline void transp4(u32 d[], unsigned int n, unsigned int m)
 {
 	u32 mask = get_mask(n);
 
···
      *  Transpose operations on 4 32-bit words (reverse order)
      */
 
-static inline void transp4x(u32 d[], unsigned int n, unsigned int m)
+static __always_inline void transp4x(u32 d[], unsigned int n, unsigned int m)
 {
 	u32 mask = get_mask(n);