hal_flash.c: delete obsolete comment

Multiple supported targets (NRF52, K64F) do not support single byte
writes.

Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
diff --git a/boot/zephyr/hal_flash.c b/boot/zephyr/hal_flash.c
index cebf161..9a78163 100644
--- a/boot/zephyr/hal_flash.c
+++ b/boot/zephyr/hal_flash.c
@@ -23,7 +23,6 @@
 
 #include "hal/hal_flash.h"
 
-/* All of the currently supported devices allow single byte writes. */
 uint8_t hal_flash_align(uint8_t flash_id)
 {
 	return FLASH_ALIGN;