udbg_adb_init() has become dependent on btext_drawchar, even when
BOOTX_TEXT support is not selected. This leads to the error below.
Make the check dependant on BOOTX_TEXT.
LD .tmp_vmlinux1
arch/powerpc/platforms/built-in.o(.toc1+0xa40): undefined
reference to `btext_drawchar'
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>