m68k: Remove inline strcpy() and strcat() implementations

m68k: Remove inline strcpy() and strcat() implementations

Gcc may replace calls to standard string functions by open code and/or
calls to other standard string functions. If the replacement function is
not available out-of-line, link errors will happen.

To avoid this, the out-of-line versions were provided by
arch/m68k/lib/string.c, but they were usually not linked in anymore as
typically none of its symbols are referenced by built-in code.
However, if any module would need them, they would not be available.

Hence remove the inline strcpy() and strcat() implementations, remove
arch/m68k/lib/string.c, and let the generic string library code handle it.

Impact on a typical kernel build seems minimal or nonexistent:

-      .text : 0x00001000 - 0x002aac74   (2728 KiB)
-      .data : 0x002ada48 - 0x00392148   ( 914 KiB)
+      .text : 0x00001000 - 0x002aacf4   (2728 KiB)
+      .data : 0x002adac8 - 0x00392148   ( 914 KiB)

See also commit e00c73ee05dc38ecaccced55d4f5fc58b0b769f7 ("m68k: Remove
inline strlen() implementation").

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>