ice: use __le16 types for explicitly Little Endian values

The ice_read_sr_aq function returns words in the Little Endian format.
Remove the need for __force and typecasting by using a local variable in
the ice_read_sr_word_aq function.

Additionally clarify explicitly that the ice_read_sr_aq function takes
storage for __le16 values instead of using u16.

Being explicit about the endianness of this data helps when using tools
like sparse to catch endian-related issues.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>