Revert "lib: bootm: add missing include"

Revert "lib: bootm: add missing include"

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This reverts commit 1e96220a5687efae2aed45ce56e143336c40d0a7.

Remove duplicated vxworks.h header.
The same change was done by
"ARM: prevent compiler warnings from bootm.c"
(sha1: 8d196e52b58d1e50a80c2f5067b201cda521c75c)

Signed-off-by: Michal Simek <michal.simek@xilinx.com>