bnxt_en: Use absolute target ns from ptp_clock_request

bnxt_en: Use absolute target ns from ptp_clock_request

There is no need to calculate the target PHC cycles required
to make phase adjustment on the PPS OUT signal. This is because
the application supplies absolute n_sec value in the future and
is already the actual desired target value.

Remove the unnecessary code.

Fixes: 9e518f25802c ("bnxt_en: 1PPS functions to configure TSIO pins")
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Tested-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20260504083611.1383776-5-pavan.chebbi@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>