Mention -B in the error message

One of possible problems of failed initialization is too hight frequency
of ISP clock. Mention using -B option as a possible solution.

Closes #1133

src/doc/avrdude.texi

@@ -3046,14 +3046,15 @@ See also: @url{http://www.libusb.org/ticket/6}
 @item
 Problem: after flashing a firmware that reduces the target's clock
 speed (e.g. through the @code{CLKPR} register), further ISP connection
-attempts fail.
+attempts fail.  Or a programmer cannot initialize communication with
+a brand new chip.
 
 Solution: Even though ISP starts with pulling @var{/RESET} low, the
-target continues to run at the internal clock speed as defined by the
-firmware running before.  Therefore, the ISP clock speed must be
-reduced appropriately (to less than 1/4 of the internal clock speed)
-using the -B option before the ISP initialization sequence will
-succeed.
+target continues to run at the internal clock speed either as defined by
+the firmware running before or as set by the factory.  Therefore, the
+ISP clock speed must be reduced appropriately (to less than 1/4 of the
+internal clock speed) using the -B option before the ISP initialization
+sequence will succeed.
 
 As that slows down the entire subsequent ISP session, it might make
 sense to just issue a @emph{chip erase} using the slow ISP clock

src/main.c

@@ -1190,9 +1190,10 @@ int main(int argc, char * argv [])
   init_ok = (rc = pgm->initialize(pgm, p)) >= 0;
   if (!init_ok) {
     pmsg_error("initialization failed, rc=%d\n", rc);
+    imsg_error("- double check the connections and try again\n");
+    imsg_error("- use -B to set lower ISP clock frequency, e.g. -B 200kHz\n");
     if (!ovsigck) {
-      imsg_error("double check connections and try again or use -F to override\n");
-      imsg_error("this check\n\n");
+      imsg_error("- use -F to override this check\n\n");
       exitrc = 1;
       goto main_exit;
     }