tcg: Fix warning (1 bit signed bitfield entry) and replace int by bool

tcg: Fix warning (1 bit signed bitfield entry) and replace int by bool

Static code analyzers complain about signed bitfields with only a single
bit. is_ld is used as a boolean value, so make it bool.

ppc64 already used bool for the 2nd argument is_ld of the local function
add_qemu_ldst_label. Modify all other TCG targets to do follow this
example.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Richard Henderson <rth@twiddle.net>