Revert "Remove some flags, kernel not booting :-/"

This reverts commit 65daba4e348aec649d15ed80dfa2d83034f54b3d.
Disable some KBUILD CFLAGS:
When -Os was removed in this change 67233197b821534a97310dd050142d7f812aa573
Some flags that were previously disabled by default are no longer disabled.
This causes stability problems and needs to be added back.  Flags
were taken from GNU documentation for what -Os disables:
http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html

Signed-off-by: Paul Beeler <sparksco@gmail.com>