ARC: strchr() bug in Big Endian configuration

For a search buffer, 2 byte aligned, strchr() was returning pointer
outside of buffer (buf - 1)

    // Input buffer (default 4 byte aigned)
    char *buffer = "1AA_";

    // actual search start (to mimick 2 byte alignment)
    char *current_line = &(buffer[2]);

    // Character to search for
    char c = 'A';

    char *c_pos = strchr(current_line, c);

    printf("%s\n", c_pos) --> 'AA_' as oppose to 'A_'

-Fix provided by Joern

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>