Use correct spelling of "U-Boot"

Correct spelling of "U-Boot" shall be used in all written text
(documentation, comments in source files etc.).

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Minkyu Kang <mk7.kang@samsung.com>
diff --git a/board/freescale/p1010rdb/README.P1010RDB-PB b/board/freescale/p1010rdb/README.P1010RDB-PB
index c5d1419..dc82f0d 100644
--- a/board/freescale/p1010rdb/README.P1010RDB-PB
+++ b/board/freescale/p1010rdb/README.P1010RDB-PB
@@ -112,14 +112,14 @@
 
 To enable SDHC in case of NOR/NAND/SPI boot
    a) For temporary use case in runtime without reboot system
-      run 'mux sdhc' in u-boot to validate SDHC with invalidating IFC.
+      run 'mux sdhc' in U-Boot to validate SDHC with invalidating IFC.
 
    b) For long-term use case
       set 'esdhc' in hwconfig and save it.
 
 To enable IFC in case of SD boot
    a) For temporary use case in runtime without reboot system
-      run 'mux ifc' in u-boot to validate IFC with invalidating SDHC.
+      run 'mux ifc' in U-Boot to validate IFC with invalidating SDHC.
 
    b) For long-term use case
       set 'ifc' in hwconfig and save it.