staging: rtl8723bs: hal: sdio_halinit: fix Comparison to NULL

This patch fixes below issue reported by checkpatch

CHECK: Comparison to NULL could be written "psta"
CHECK: Comparison to NULL could be written "psta"

Signed-off-by: Hariprasad Kelam <hariprasad.kelam@gmail.com>
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changes in v2: Send proper patch with out corruption
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>