OMAP: iovmm: fix SW flags passed by user

Commit d038aee2
"omap: iovmm: don't check 'da' to set IOVMF_DA_FIXED flag",
changes iovmm to receive flags specified by user, however
the upper 16 bits of the flags are wiped by iovmm itself.

This fixes IOVMF_DA_FIXED flags from being lost, and lets the user
map its desired "device addresses".

Signed-off-by: Omar Ramirez Luna <omar.ramirez@ti.com>
Acked-by: Hiroshi DOYU <Hiroshi.DOYU@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>