flash/nor/nrf5: drop useless for cycle condition

Commit [1] added a break on error to the nrf5_erase() sector loop
and the checking of the res value became useless in the for loop condition.

Removing nrf5_get_probed_chip_if_halted() later in [2]
dropped res initialization and clang static analyser complains
  "The left operand of '==' is a garbage value"

Drop the useless test!

Fixes: [1] commit 491636c ("flash/nor/nrf5: check protection before flash erase/write on nRF51")
Fixes: [2] commit 2db325f ("flash/nor/nrf5: drop nrf5_get_probed_chip_if_halted()")
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Change-Id: Ife6071c509719f8d7dc312fe9a780bdcf2575f69
Reviewed-on: https://review.openocd.org/c/openocd/+/8174
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

src/flash/nor/nrf5.c

@@ -1071,7 +1071,7 @@ static int nrf5_erase(struct flash_bank *bank, unsigned int first,
 	}
 
 	/* For each sector to be erased */
-	for (unsigned int s = first; s <= last && res == ERROR_OK; s++) {
+	for (unsigned int s = first; s <= last; s++) {
 
 		if (chip->features & NRF5_FEATURE_SERIES_51
 				&& bank->sectors[s].is_protected == 1) {