net: ipa: always inline ipa_aggr_granularity_val()

It isn't required, but all callers of ipa_aggr_granularity_val()
pass a constant value (IPA_AGGR_GRANULARITY) as the usec argument.
Two of those callers are in ipa_validate_build(), with the result
being passed to BUILD_BUG_ON().

Evidently the "sparc64-linux-gcc" compiler (at least) doesn't always
inline ipa_aggr_granularity_val(), so the result of the function is
not constant at compile time, and that leads to build errors.

Define the function with the __always_inline attribute to avoid the
errors. We can see by inspection that the value passed is never
zero, so we can just remove its WARN_ON() call.

Fixes: 5bc5588466a1f ("net: ipa: use WARN_ON() rather than assertions")
Reported-by: kernel test robot <[e-mail]>
Signed-off-by: Alex Elder <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ipa/ipa_main.c

···
 /* Compute the value to use in the COUNTER_CFG register AGGR_GRANULARITY
  * field to represent the given number of microseconds.  The value is one
  * less than the number of timer ticks in the requested period.  0 is not
- * a valid granularity value.
+ * a valid granularity value (so for example @usec must be at least 16 for
+ * a TIMER_FREQUENCY of 32000).
  */
-static u32 ipa_aggr_granularity_val(u32 usec)
+static __always_inline u32 ipa_aggr_granularity_val(u32 usec)
 {
-	WARN_ON(!usec);
-
 	return DIV_ROUND_CLOSEST(usec * TIMER_FREQUENCY, USEC_PER_SEC) - 1;
 }