linux-user: Fix incorrect TARGET_BLKBSZGET, TARGET_BLKBSZSET

linux-user: Fix incorrect TARGET_BLKBSZGET, TARGET_BLKBSZSET

The definitions for the ioctl numbers TARGET_BLKBSZGET and
TARGET_BLKBSZSET had the wrong size parameters (they are defined
with size_t, not int, even though the ioctl implementations themselves
read and write integers). Since commit 354a0008 we now have an
ioctl wrapper definition for BLKBSZGET and so on an x86-64-to-x86-64
linux-user binary we were triggering the mismatch warning in
syscall_init().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>