linux-user: Add configure check for linux/fiemap.h and IOC_FS_FIEMAP

Add a configure check for the existence of linux/fiemap.h and the
IOC_FS_FIEMAP ioctl. This fixes a compilation failure on Linux
systems which don't have that header file.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
