xsk: add linux/vmalloc.h to xsk.c

Fix the failure of the compilation under the sh4.

Because we introduced remap_vmalloc_range() earlier, this has caused
the compilation failure on the sh4 platform. So this introduction of the
header file of linux/vmalloc.h.

config: sh-allmodconfig (https://download.01.org/0day-ci/archive/20230221/[email protected]/config)
compiler: sh4-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/commit/?id=9f78bf330a66cd400b3e00f370f597e9fa939207
        git remote add net-next https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git
        git fetch --no-tags net-next master
        git checkout 9f78bf3
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=sh olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=sh SHELL=/bin/bash net/

Fixes: 9f78bf3 ("xsk: support use vaddr as ring")
Signed-off-by: Xuan Zhuo <[email protected]>
Reported-by: kernel test robot <[email protected]>
Link: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

net/xdp/xsk.c

@@ -22,6 +22,7 @@
 #include <linux/net.h>
 #include <linux/netdevice.h>
 #include <linux/rculist.h>
+#include <linux/vmalloc.h>
 #include <net/xdp_sock_drv.h>
 #include <net/busy_poll.h>
 #include <net/xdp.h>