staging: rts5208: pass timeout as HZ independent value

schedule_timeout takes a timeout in jiffies but the code currently is
passing in a constant POLLING_INTERVAL which makes this timeout HZ
dependent, so pass it through msecs_to_jiffies() to fix this up.

patch was compile tested for x86_64_defconfig + CONFIG_STAGING=y,
CONFIG_RTS5208=m

Patch is against 4.0-rc5 (localversion-next is -next-20150527)

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>