x86: Fix indirect jmp warning in zimage.c

This fixes the following warning:

zimage.c:312: Warning: indirect jmp without `*'

Also fixed these warnings to keep checkpatch quiet:

warning: arch/x86/lib/zimage.c,311: unnecessary whitespace before a quoted newline
warning: arch/x86/lib/zimage.c,312: unnecessary whitespace before a quoted newline
warning: arch/x86/lib/zimage.c,313: unnecessary whitespace before a quoted newline

Signed-off-by: Simon Glass <sjg@chromium.org>