hw/char/riscv_htif: Fix the console syscall on big endian hosts

hw/char/riscv_htif: Fix the console syscall on big endian hosts

Values that have been read via cpu_physical_memory_read() from the
guest's memory have to be swapped in case the host endianess differs
from the guest.

Fixes: a6e13e31d5 ("riscv_htif: Support console output via proxy syscall")
Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-Id: <20230721094720.902454-3-thuth@redhat.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
(cherry picked from commit 058096f1c55ab688db7e1d6814aaefc1bcd87f7a)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>