dm: spi: Add logging of some return values

When SPI flash operations fail it is helpful to be able to see the error
codes and where they are generated. Add logging to capture this
information for read operations.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/mtd/spi/spi_flash.c b/drivers/mtd/spi/spi_flash.c
index 7113c85..9230060 100644
--- a/drivers/mtd/spi/spi_flash.c
+++ b/drivers/mtd/spi/spi_flash.c
@@ -471,14 +471,14 @@
 	u8 cmdsz;
 	u32 remain_len, read_len, read_addr;
 	int bank_sel = 0;
-	int ret = -1;
+	int ret = 0;
 
 	/* Handle memory-mapped SPI */
 	if (flash->memory_map) {
 		ret = spi_claim_bus(spi);
 		if (ret) {
 			debug("SF: unable to claim SPI bus\n");
-			return ret;
+			return log_ret(ret);
 		}
 		spi_xfer(spi, 0, NULL, NULL, SPI_XFER_MMAP);
 		spi_flash_copy_mmap(data, flash->memory_map + offset, len);
@@ -501,7 +501,7 @@
 #ifdef CONFIG_SPI_FLASH_BAR
 		ret = write_bar(flash, read_addr);
 		if (ret < 0)
-			return ret;
+			return log_ret(ret);
 		bank_sel = flash->bank_curr;
 #endif
 		remain_len = ((SPI_FLASH_16MB_BOUN << flash->shift) *
@@ -531,7 +531,7 @@
 	ret = clean_bar(flash);
 #endif
 
-	return ret;
+	return log_ret(ret);
 }
 
 #ifdef CONFIG_SPI_FLASH_SST