boot/syslinux: fix build of efi part with gnu-efi 3.0.10

boot/syslinux: fix build of efi part with gnu-efi 3.0.10

The following defconfig:

BR2_x86_i686=y
BR2_TOOLCHAIN_EXTERNAL=y
BR2_TOOLCHAIN_EXTERNAL_DOWNLOAD=y
BR2_TOOLCHAIN_EXTERNAL_URL="http://toolchains.bootlin.com/downloads/releases/toolchains/x86-i686/tarballs/x86-i686--glibc--bleeding-edge-2018.11-1.tar.bz2"
BR2_TOOLCHAIN_EXTERNAL_GCC_8=y
BR2_TOOLCHAIN_EXTERNAL_HEADERS_4_14=y
BR2_TOOLCHAIN_EXTERNAL_CUSTOM_GLIBC=y
BR2_TOOLCHAIN_EXTERNAL_CXX=y
BR2_INIT_NONE=y
BR2_TARGET_SYSLINUX=y
BR2_TARGET_SYSLINUX_EFI=y

fails to build due to missing setjmp/longjmp definitions, which is a
consequence of a change introduced between gnu-efi 3.0.9 and 3.0.10.

This build failure is fixed by adding another syslinux paytch, which
has been submitted upstream.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>