convert.c: Fix return type of git_path_check_eol()

convert.c: Fix return type of git_path_check_eol()

The git_path_check_eol() function converts a string value to the
corresponding 'enum eol' value. However, the function is currently
declared to return an 'enum crlf_action', which causes sparse to
complain thus:

        SP convert.c
    convert.c:736:50: warning: mixing different enum types
    convert.c:736:50:     int enum crlf_action  versus
    convert.c:736:50:     int enum eol

In order to suppress the warning, we simply correct the return type
in the function declaration.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>