RISV-V: fix setting timecmp_lo

[exokortex]

Setting timecmp_lo should not copy timecmp_lo to timecmp_hi. Fixed by taking the upper 32 bits instead of lower ones.

[michaeljclark]

Good spotting. Thanks!

I merged this into the qemu-2.13-for-upstream and have rebuilt the riscv-all branch.

I expanded the commit log message, added your name and email so that we conform to upstream QEMU patch submission guidelines. See here:

• https://github.com/riscv/riscv-qemu/commits/qemu-2.13-for-upstream (https://github.com/riscv/riscv-qemu/commit/9cf34d14fee5a9f7267f15d58417833bdb507246)

I tweaked the patch a little to use a shift because large constant synthesis is tricky on some platforms. For example we can avoid the extra li (Load Immediate) on RISC-V and avoid movabs on x86_64 which embeds a large 64-bit constant in the instruction. Using sll/shl is a tiny bit smaller:

• https://cx.rv8.io/g/YTEwbt