s390/startup: purge obsolete .gitignore patterns

sizes.h and vmlinux.scr.lds are not generated since commit 369f91c3
("s390/decompressor: rework uncompressed image info collection").

vmlinux.bin.full is not generated since commit 183ab05f ("s390: get
rid of the first mb of uncompressed image").
Signed-off-by: NVasily Gorbik <gor@linux.ibm.com>

arch/s390/boot/compressed/.gitignore

-sizes.h
 vmlinux
 vmlinux.lds
-vmlinux.scr.lds
-vmlinux.bin.full