re: wifi: rt2x00: add TX LOFT calibration for MT7620

["Colin King (gmail)" <colin.i.king@gmail.com>]

Hi,

I noticed a signed / unsigned comparison warning when building 
linux-next with clang. I believe it was introduced in the following commit:

commit dab902fe1d29dc0fa1dccc8d13dc89ffbf633881
Author: Tomislav Požega <pozega.tomislav@gmail.com>
Date:   Sat Sep 17 21:28:43 2022 +0100

     wifi: rt2x00: add TX LOFT calibration for MT7620


The warning is as follows:

drivers/net/wireless/ralink/rt2x00/rt2800lib.c:9472:15: warning: result 
of comparison of constant -7 with expression of type 'char' is always 
false [-Wtautological-constant-out-of-range-compare]
         gerr = (gerr < -0x07) ? -0x07 : (gerr > 0x05) ? 0x05 : gerr;
                 ~~~~ ^ ~~~~~
drivers/net/wireless/ralink/rt2x00/rt2800lib.c:9476:15: warning: result 
of comparison of constant -31 with expression of type 'char' is always 
false [-Wtautological-constant-out-of-range-compare]
         perr = (perr < -0x1f) ? -0x1f : (perr > 0x1d) ? 0x1d : perr;
                 ~~~~ ^ ~~~~~

The variables gerr and perr are declared as a char, which in this case 
seems to be defaulting to signed on the clang build for x86-64 and hence 
this warning. I suspect making it signed char will do the trick, but I 
wanted to flag this up in-case there were some other issues with making 
them signed.

Colin