mmc: sdhci-pci-gli: fix GL9750 DMA write corruption

mmc: sdhci-pci-gli: fix GL9750 DMA write corruption

The GL9750 SD host controller has intermittent data corruption during
DMA write operations. The GM_BURST register's R_OSRC_Lmt field
(bits 17:16), which limits outstanding DMA read requests from system
memory, is not being cleared during initialization. The Windows driver
sets R_OSRC_Lmt to zero, limiting requests to the smallest unit.

Clear R_OSRC_Lmt to match the Windows driver behavior. This eliminates
write corruption verified with f3write/f3read tests while maintaining
DMA performance.

Cc: stable@vger.kernel.org
Fixes: e51df6ce668a ("mmc: host: sdhci-pci: Add Genesys Logic GL975x support")
Closes: https://lore.kernel.org/linux-mmc/33d12807-5c72-41ce-8679-57aa11831fad@linux.dev/
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Matthew Schwartz <matthew.schwartz@linux.dev>
Reviewed-by: Ben Chuang <ben.chuang@genesyslogic.com.tw>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>