change riscv-isa-run to spike in documentation

README

@@ -25,7 +25,7 @@ install path, and that the riscv-fesvr package is installed there.
 Compiling and Running a Simple C Program
 --------------------------------------------------------------------------
 
-Install riscv-isa-run (see Build Steps), riscv-gcc, and riscv-pk.
+Install spike (see Build Steps), riscv-gcc, and riscv-pk.
 
 Write a short C program and name it hello.c.  Then, compile it into a RISC-V
 ELF binary named hello:
@@ -34,7 +34,7 @@ ELF binary named hello:
 
 Now you can simulate the program atop the proxy kernel:
 
- % riscv-isa-run pk hello
+ % spike pk hello
 
 --------------------------------------------------------------------------
 Simulating a New Instruction

riscv/spike.cc

@@ -13,7 +13,7 @@
 
 static void help()
 {
-  fprintf(stderr, "usage: riscv-isa-run [host options] <target program> [target options]\n");
+  fprintf(stderr, "usage: spike [host options] <target program> [target options]\n");
   fprintf(stderr, "Host Options:\n");
   fprintf(stderr, "  -p <n>             Simulate <n> processors\n");
   fprintf(stderr, "  -m <n>             Provide <n> MB of target memory\n");