wil6210: validate wil_pmc_alloc parameters

num_descriptors and descriptor_size needs to be
checked for:
1) not being negative values
2) no overflow occurs when these are multiplied
together as done in wil_pmc_read.
An overflow of two signed integers is undefined
behavior.

Change-Id: I669dc12a17b3102a7fd7f28e8c78843e3e3f9764
Signed-off-by: Maya Erez <qca_merez@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
Git-commit: 1db226ffe1c2ab900cffb1d71f042e565f77775d
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git


CRs-Fixed: 1077174
Signed-off-by: Maya Erez <merez@codeaurora.org>