Fix clippy warnings (#150)

Author: usbalbin

src/flash.rs

@@ -58,7 +58,7 @@ pub struct FlashWriter<'a, const SECTOR_SZ_KB: u32> {
     flash_sz: FlashSize,
     verify: bool,
 }
-impl<'a, const SECTOR_SZ_KB: u32> FlashWriter<'a, SECTOR_SZ_KB> {
+impl<const SECTOR_SZ_KB: u32> FlashWriter<'_, SECTOR_SZ_KB> {
     #[allow(unused)]
     fn unlock_options(&mut self) -> Result<()> {
         // Check if flash is busy

src/rcc/mod.rs

@@ -414,7 +414,7 @@ impl Rcc {
         let us_per_s = 1_000_000;
         // Number of cycles @ sys_freq for 1us, rounded up, this will
         // likely end up being 2us since the AHB prescaler is changed
-        let delay_cycles = (sys_freq + us_per_s - 1) / us_per_s;
+        let delay_cycles = sys_freq.div_ceil(us_per_s);
         cortex_m::asm::delay(delay_cycles);
 
         self.rb