linux-mips-low.c: Fix type of mips_add_watchpoint parameter

linux-mips-low.c: Fix type of mips_add_watchpoint parameter

Fixes

/home/simark/src/binutils-gdb/gdb/gdbserver/linux-mips-low.c: In function ‘void mips_add_watchpoint(arch_process_info*, CORE_ADDR, int, int)’:
/home/simark/src/binutils-gdb/gdb/gdbserver/linux-mips-low.c:368:19: error: invalid conversion from ‘int’ to ‘target_hw_bp_type’ [-fpermissive]
   new_watch->type = watch_type;
                   ^

gdb/gdbserver/ChangeLog:

	* linux-mips-low.c (mips_linux_new_thread): Change type of
	watch_type to enum target_hw_bp_type.