ash: expand: Fixed "$@" expansion when EXP_FULL is false

ash: expand: Fixed "$@" expansion when EXP_FULL is false

Upstream commit:

    Date: Thu, 1 Jan 2015 07:53:10 +1100
    expand: Fixed "$@" expansion when EXP_FULL is false

    The commit 3c06acdac0b1ba0e0acdda513a57ee6e31385dce ([EXPAND]
    Split unquoted $@/$* correctly when IFS is set but empty) broke
    the case where $@ is in quotes and EXP_FULL is false.

    In that case we should still emit IFS as field splitting is not
    performed.

    Reported-by: Juergen Daubert <jue@jue.li>
    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>