configs: sheevaplug disable EFI_UNICODE_CAPITALIZATION

With upcoming patches u-boot.kwb gets too large.

Save 3740 bytes in u-boot.kwb by disabling Unicode support in the UEFI
sub-system.
Signed-off-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>

configs/sheevaplug_defconfig

@@ -46,3 +46,4 @@ CONFIG_DM_USB=y
 CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_STORAGE=y
 CONFIG_LZMA=y
+# CONFIG_EFI_UNICODE_CAPITALIZATION is not set