Fix RISC-V Linux build again (#215)

PR #204 broke the RISC-V
build by including for a second time a header file that currently
only exists in the RISC-V Android NDK.  The header is not yet
available in mainstream Linux distributions.  The header in question,
<sys/hwprobe.h>, is already included when building for Android
at the top of riscv-hw.c so the second include is unnecessary and
can be safely removed.

Author: markdryan

src/riscv/linux/riscv-hw.c

@@ -14,7 +14,6 @@
 #endif
 
 #include <sched.h>
-#include <sys/hwprobe.h>
 
 #include <cpuinfo/log.h>
 #include <riscv/api.h>