sh: Add 64-bit time types from kernel

sh: Add 64-bit time types from kernel

Building uclibc 1.0.37 for SuperH architecture with linux-headers 5.10.7
fails at libpthread level due to missing time-related data structures,
usually defined by the kernel.

Define those missing data structures in SuperH-specific kernel_types.h.

Context: building for sh4eb-r2d[1] and sh4-r2d[1] boards emulations for
QEMU using the buildroot image generation tool.

Regarding the issue, a patch[3] was already issued in the kernel some
time ago, which aimed to solve precisely this problem. After coming up
with a quick and dirty patch for buildroot modifying Linux headers[4],
some discussion was sparked on the subject with Linux folks[5]. Some
analyzing later, conclusion was that:
1) Previously mentioned patch[4] was fixing the symptom, not the ill
2) SuperH-specific code in uclibc could be patched instead, to solve
   the problem for other use cases (e.g. building just a toolchain)

[1] https://git.buildroot.net/buildroot/tree/configs/qemu_sh4eb_r2d_defconfig?h=2020.02.9
[2] https://git.buildroot.net/buildroot/tree/configs/qemu_sh4_r2d_defconfig?h=2020.02.9
[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fc94cf2092c7c1267fa2deb8388d624f50eba808
[4] https://git.buildroot.net/buildroot/commit/?id=742f37de8d0e3797698411dfc6a63bd7e98aafe2
[5] https://patchwork.kernel.org/project/linux-sh/patch/20210123165652.10884-1-geoffrey.legourrierec@gmail.com/

Signed-off-by: Geoffrey Le Gourriérec <geoffrey.legourrierec@gmail.com>