Renamed assembly initialization code to _entry instead of _start, to avoid confusing with start() C function

entry.S

@@ -1,6 +1,6 @@
 .section .text
-.globl _start
-_start:
+.globl _entry
+_entry:
     # Both call and j will work here, but since ra will be cleared,
     # we will need a jump instruction back (from _clear) to continue.
     call _clear

link.ld

@@ -1,5 +1,5 @@
-OUTPUT_ARCH(riscv)
-ENTRY(_start)
+OUTPUT_ARCH( "riscv" )
+ENTRY( _entry ) /* See: entry.S */
 
 SECTIONS
 {