support/testing: test_f2fs: bump to kernel 4.19.204

support/testing: test_f2fs: bump to kernel 4.19.204

The kernel 4.16.7 curently used by the test doesn't build with host
gcc >= 10 due the gcc default -fno-common. See GCC 10 porting guide [1].

/usr/bin/ld: scripts/dtc/dtc-parser.tab.o:(.bss+0x20): multiple definition of `yylloc'; scripts/dtc/dtc-lexer.lex.o:(.bss+0x0): first defined here

Bump to the next LTS release.

[1] https://gcc.gnu.org/gcc-10/porting_to.html

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>