spi: stm32h7: replace private SPI_1HZ_NS with NSEC_PER_SEC

Replace SPI_1HZ_NS private constant with NSEC_PER_SEC, which is easier
to read and understand.
Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
Link: https://lore.kernel.org/r/1612551572-495-8-git-send-email-alain.volmat@foss.st.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-stm32.c

@@ -162,8 +162,6 @@
 #define SPI_3WIRE_TX		3
 #define SPI_3WIRE_RX		4
 
-#define SPI_1HZ_NS		1000000000
-
 /*
  * use PIO for small transfers, avoiding DMA setup/teardown overhead for drivers
  * without fifo buffers.
@@ -1525,7 +1523,7 @@ static void stm32h7_spi_data_idleness(struct stm32_spi *spi, u32 len)
 
 	cfg2_clrb |= STM32H7_SPI_CFG2_MIDI;
 	if ((len > 1) && (spi->cur_midi > 0)) {
-		u32 sck_period_ns = DIV_ROUND_UP(SPI_1HZ_NS, spi->cur_speed);
+		u32 sck_period_ns = DIV_ROUND_UP(NSEC_PER_SEC, spi->cur_speed);
 		u32 midi = min_t(u32,
 				 DIV_ROUND_UP(spi->cur_midi, sck_period_ns),
 				 FIELD_GET(STM32H7_SPI_CFG2_MIDI,