of: base: Fix spelling issue with function param 'prop'

of: base: Fix spelling issue with function param 'prop'

Fixes the following W=1 kernel build warning(s):

 drivers/of/base.c:1781: warning: Function parameter or member 'prop' not described in '__of_add_property'
 drivers/of/base.c:1781: warning: Excess function parameter 'prob' description in '__of_add_property'
 drivers/of/base.c:1804: warning: Function parameter or member 'prop' not described in 'of_add_property'
 drivers/of/base.c:1804: warning: Excess function parameter 'prob' description in 'of_add_property'
 drivers/of/base.c:1855: warning: Function parameter or member 'prop' not described in 'of_remove_property'
 drivers/of/base.c:1855: warning: Excess function parameter 'prob' description in 'of_remove_property'

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: devicetree@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210329152435.900225-1-lee.jones@linaro.org
Signed-off-by: Rob Herring <robh@kernel.org>